Arista EOS/Networking Tips by Solomon Yang

1/13/2022

Arista EOS: traffic tool on Linux

https://eos.arista.com/traffic-generator-on-arista/

iperf

but seeing time out error? iptables issue? need to check later

ethxmit

12/03/2021

Arista EOS - CoppSystemEgressTrap drop

On Arista 7280*R* series routers, if you are seeing high # of CoppSystemEgressTrap drop in the output of "show cpu counters queue", the most likely reason is that, there are some packets size are larger than the egress interface configured size.

smv550.08:42:39#show cpu counters queue summary | nz
Aggregate CPU counters:
This indicates the sum of port-dependent queue counters across all input ports.
CoPP Class Pkts Octets DropPkts DropOctets
Aggregate
-------------------------------------------------------------------------------------------------------
CoppSystemBgp 14358 1141461 0 0
CoppSystemEgressTrap 10688 97079104 228017 2071078411

10/19/2021

Arista MLAG vs unstable STP

Before reloading an MLAG peer switch to perform an upgrade/downgrade, one of the key check-ups is to make sure the STP is restartable. Otherwise, traffic loss is expected.

bn303.08:17:13(s1)#sh spanning-tree instance detail | grep rest

Stp agent restartable : False

Oct 19 08:16:15 bn303.aristanetworks.com Stp: %SPANTREE-6-STABLE_CHANGE: Stp state is now not stable

Oct 19 08:17:06 bn303.aristanetworks.com Stp: %SPANTREE-6-STABLE_CHANGE: Stp state is now stable

To find out which ports causing this issue, by using CLI - sh spanning-tree topology status detail, to search most recently changed ports, like

bn303.08:22:51(s1)#sh spanning-tree topology status detail | more

Topology: Cist

Mapped Vlans: 1,4080-4087

Cpu: forwarding (1 changes, last 7:40:20 ago)

Ethernet8/16/1: forwarding (3 changes, last 0:23:10 ago) <<<

PeerEthernet8/16/1: forwarding (3 changes, last 0:23:10 ago) <<<

The reason of unstable STP is because, the MLAG switch keeps receiving its own (actually from the active MLAG peer) BPDU and can't form an agreement. The solution can be either, shutting down the port or put it as no-switching port.

8/12/2021

EOS device boots into a weird state - [PyServer ar.Aaa not responding, still trying -- is it running?]

One possible reason is that, there is an unknown registered toggle switch.....

Arista Networks EOS 4.22.4M
localhost login: admin
[PyServer ar.Aaa not responding, still trying -- is it running?]
[PyServer ar.Aaa not responding, still trying -- is it running?]

...<snip> reboot....

Welcome to Arista Networks EOS 4.22.4M

Failed(tg != toggles.end()) Toggle #BfdPeerDeferredDeletion not registered

.....

...reboot....

Press Control-C now to enter Aboot shell

...press ctrl-c here to enter aboot mode...

^CWelcome to Aboot.

Aboot# cd /mnt/flash

Aboot# mv toggle_override toggle_override.old

! get rid of /mnt/flash/toggle_override file

Aboot# reboot

....

.... now it is good....

6/13/2021

MPLS Hashing: Control Word and Entropy Label

A good presentation on this topic: https://ripe66.ripe.net/presentations/141-RIPE66_Understanding_MPLS_Hashing-Snijders.pdf

MPLS Lable doesn't have encapsulated protocol information. So after the bottom label, 2 possibilities:

IPv4/v6 packets if L3VPN, the 1st 4-bit is ipVersion, 4=ipv4, 6=ipv6
Ethernet frames if L2VPN, the 1st 48-bit is dstMAC

Along the LSP, if P routers like to do ECMP by hashing, it has to guess like above to do hashing the 5-tuple fields (src/dstAddr, src/dstPort, protoNum)
So the problem happens if the dstMac starts with 4 or 6

The solution for the above issue is MPLS control word (RFC 4385, Feb 2006), a 4-byte all-zero (same length as a label) control word after the bottom label.

Arista EOS 4.21.3F: Configurable L2 EVPN MPLS control word

mpls evpn; label-stack control-word

Arista EOS 4.22.1F: Control Word support on LDP Pseudowire

mpls ldp; pseudowire <name>; control-word

So the MPLS control word is to prevent incorrect hashing. How does the LSR do the load-balancing? The answer is Entropy Label (RFC 6790, Nov 2012)

Increase the label stack by 2: 1 for ELI (entropy label indicator = 7), 1 for EL (entropy label)
Aristea EOS 4.26.0F: LDP Entropy Label Support

4.25.2F: LSR support
4.26.0F: LER support
mpls ldp; entropy-label

This feature has a limitation: PHP LSR can't pop ELI + EL labels, so has to rely on LER to pop up [ELI, ELI, VPN] labels.

Another solution is FAT - Flow Aware Transport on LDP pseudowires (4.24.0F) based on RFC 6391

mpls ldp; pseudowire; pseudowire <name>; label flow

5/27/2021

Troubleshooting Arista EOS EVPN VPWS (1)

This blog provides troubleshooting information for common problems with Arista EVPN MPLS VPWS. It covers the following error:

Status: CLI conflict
Status: Admin down
Status: Interface unavailable
Status: No remote
Status: Unprogrammed local connector

Most of the issues start with down state in the output of "show patch panel" like below:

RR1-PE5-wa465.11:42:56#sh patch panel
Patch Connector Status
---------------------------- ------------------------------------------------------- ------
pbVpws-PE5:e471--PE1:e1312 1: BGP VPWS custAB Pseudowire PE5:e471--PE1:e1312 Down
2: Ethernet47/1

And command - "show patch panel <name> details" shows the detailed error reason:

RR1-PE5-wa465.14:58:02#sh patch panel pbVpws-PE5:e471--PE1:e1312 detail

......

Patch: pbVpws-PE5:e471--PE1:e1312, Status: Down

Connector 1: BGP VPWS custAB Pseudowire PE5:e471--PE1:e1312

Status: Interface unavailable

Local MPLS label: 100004

EVPN VPWS type: port-based

Connector 2: Ethernet47/1

Status: Interface mode

The following error status means a local misconfiguration most likely.

Ethernet side:

Status: CLI conflict

Possible reason: duplicated patch panel entries for the same ethernet interface

Status: Admin down

Check the interface status, to make sure is up

Pseudowire side:

Status: Interface unavailable

Possible reason: make sure "no switchport" under interface

After the local configuration is corrected, check the output of "show bgp evpn route-type auto-dis next-hop 0.0.0.0". This is to check if the locally originated BGP EVPN prefixes are advertised out to BGP peers.

RR1-PE5-wa465.14:58:14#show bgp evpn route-type auto-discovery next-hop 0.0.0.0

....

AS Path Attributes: Or-ID - Originator ID, C-LST - Cluster List, LL Nexthop - Link Local Nexthop

Network Next Hop Metric LocPref Weight Path

* > RD: 100.250.250.5:100 auto-discovery 50471 0000:0000:0000:0000:0000

- - - 0 i

RR1-PE5-wa465.15:07:10#show bgp evpn route-type auto-discovery next-hop 0.0.0.0 detail

BGP routing table information for VRF default

Router identifier 100.250.250.5, local AS number 65000

BGP routing table entry for auto-discovery 50471 0000:0000:0000:0000:0000, Route Distinguisher: 100.250.250.5:100

Paths: 1 available

Local

- from - (0.0.0.0)

Origin IGP, metric -, localpref -, weight 0, valid, local, best

Extended Community: Route-Target-AS:65000:100 TunnelEncap:tunnelTypeMpls L2 Attributes: control word

MPLS label: 100004

The most important information as highlighted above is the ETID/PW ID. And compare it with the definition of PW PE5:e471--PE1:e1312

RR1-PE5-wa465.15:06:29#show bgp evpn instance vpws custAB

...

Pseudowire PE5:e471--PE1:e1312

Status: up

VPWS label: 100004

Local VPWS ID: 50471

Remote VPWS ID: 101312

After this point, you are pretty sure this end of PW is good.

But if you are seeing the error status as "No remote", the device may have an issue with remote PW.

Patch: pbVpws-PE5:e471--PE1:e1312, Status: Down

Connector 1: BGP VPWS custAB Pseudowire PE5:e471--PE1:e1312

Status: No remote

Local MPLS label: 100004

EVPN VPWS type: port-based

Connector 2: Ethernet47/1

Status: Unprogrammed local connector

Now let's check the router knows how to reach PW with VPWS ID 101312.

RR1-PE5-wa465.15:13:06#show bgp evpn route-type auto-discovery | grep 101312

RR1-PE5-wa465.15:13:10#

Clearly, the router has no EVPN AD prefix with ETID 101312, so it doesn't how to reach. The next step is to log in to the other end of PW to figure out why by following the above steps. For example, the remote PW should be from NH 100.250.250.11

PE3-lp232.22:00:03#sh bgp evpn route-type auto-discovery next-hop 100.250.250.11

...

Network Next Hop Metric LocPref Weight Path

* >Ec RD: 100.250.250.11:100 auto-discovery 101331 0000:0000:0000:0000:0000

100.250.250.11 - 100 0 i Or-ID: 100.250.250.11 C-LST: 100.250.250.6

From the above output, the PE1(100.250.250.11) sends out an AD prefix with ETID 101331, not 101311.

And sometimes, you may face traffic issues even all the PW and patch panels are UP!! That's because the BGP EVPN AD prefixes only contain the local ETID/PW id, no the expected remote one. There is no way to ensure consistency.

Reference:

https://eos.arista.com/eos-4-24-2f/evpn-mpls-virtual-private-wire-service-vpws/

5/20/2021

"Pending BGP Convergence" and invalid on MPLS/SR/EVPN BGP RR

On a BGP EVPN RR, I am seeing some EVPN routes are marked as "Pending BGP Convergence" as below:

RR1.12:01:04#sh bgp evpn
BGP routing table information for VRF default
Router identifier 100.250.250.5, local AS number 65000
Route status codes: s - suppressed, * - valid, > - active, E - ECMP head, e - ECMP
S - Stale, c - Contributing to ECMP, b - backup
% - Pending BGP convergence
Origin codes: i - IGP, e - EGP, ? - incomplete
AS Path Attributes: Or-ID - Originator ID, C-LST - Cluster List, LL Nexthop - Link Local Nexthop
Network Next Hop Metric LocPref Weight Path
% RD: 100.250.250.11:100 auto-discovery 110100 0000:0000:0000:0000:0000
100.250.250.11 - 100 0 i
% RD: 100.250.250.12:100 auto-discovery 120100 0000:0000:0000:0000:0000
100.250.250.12 - 100 0 i

The reason is "invalid" in the output of show bgp evpn detail

RR1.12:10:27#sh bgp evpn route-type auto-discovery detail

BGP routing table information for VRF default

Router identifier 100.250.250.5, local AS number 65000

BGP routing table entry for auto-discovery 110100 0000:0000:0000:0000:0000, Route Distinguisher: 100.250.250.11:100

Paths: 1 available

Local (Received from a RR-client)

100.250.250.11 from 100.250.250.11 (100.250.250.11)

Origin IGP, metric -, localpref 100, weight 0, invalid, internal, pending resolution

Extended Community: Route-Target-AS:65000:100 TunnelEncap:tunnelTypeMpls L2 Attributes: control word

BGP routing table entry for auto-discovery 120100 0000:0000:0000:0000:0000, Route Distinguisher: 100.250.250.12:100

Paths: 1 available

Local (Received from a RR-client)

100.250.250.12 from 100.250.250.12 (100.250.250.12)

Origin IGP, metric -, localpref 100, weight 0, invalid, internal, pending resolution

Extended Community: Route-Target-AS:65000:100 TunnelEncap:tunnelTypeMpls L2 Attributes: control word

Here is the BGP configuration:

RR1.11:59:52#sh run sec router bgp

router bgp 65000

router-id 100.250.250.5

no bgp default ipv4-unicast

neighbor RRC peer group

neighbor RRC remote-as 65000

neighbor RRC update-source Loopback0

neighbor RRC route-reflector-client

neighbor RRC send-community extended

neighbor 100.250.250.11 peer group RRC

neighbor 100.250.250.12 peer group RRC

neighbor 100.250.250.21 peer group RRC

neighbor 100.250.250.22 peer group RRC

address-family evpn

neighbor RRC activate

Add "neighbor default encapsulation mpls next-hop-self source-interface Loopback0" under EVPN AF

RR1.12:20:00(config)#router bgp 65000

RR1.12:20:02(config-router-bgp)#address-family evpn

RR1.12:20:04(config-router-bgp-af)#neighbor default encapsulation mpls next-hop-self source-interface Loopback0

One prefix shows "* >" - valid. One shows no code

RR1.12:20:10#sh bgp evpn

BGP routing table information for VRF default

Router identifier 100.250.250.5, local AS number 65000

Route status codes: s - suppressed, * - valid, > - active, E - ECMP head, e - ECMP

S - Stale, c - Contributing to ECMP, b - backup

% - Pending BGP convergence

Origin codes: i - IGP, e - EGP, ? - incomplete

AS Path Attributes: Or-ID - Originator ID, C-LST - Cluster List, LL Nexthop - Link Local Nexthop

Network Next Hop Metric LocPref Weight Path

RD: 100.250.250.11:100 auto-discovery 110100 0000:0000:0000:0000:0000

100.250.250.11 - 100 0 i

* > RD: 100.250.250.12:100 auto-discovery 120100 0000:0000:0000:0000:0000

100.250.250.12 - 100 0 i

Details still shows "invalid"

RR1.12:22:09#sh bgp evpn route-type auto-discovery rd 100.250.250.11:100 detail

BGP routing table information for VRF default

Router identifier 100.250.250.5, local AS number 65000

BGP routing table entry for auto-discovery 110100 0000:0000:0000:0000:0000, Route Distinguisher: 100.250.250.11:100

Paths: 1 available

Local (Received from a RR-client)

100.250.250.11 from 100.250.250.11 (100.250.250.11)

Origin IGP, metric -, localpref 100, weight 0, invalid, internal

Extended Community: Route-Target-AS:65000:100 TunnelEncap:tunnelTypeMpls L2 Attributes: control word

MPLS label: 132768

No tunnel endpoint in "show tunnel rib brief"

RR1.12:22:50#show tunnel rib brief | grep 250.250.1

100.250.250.1/32 IS-IS SR IPv4 6 65 115 20

100.250.250.12/32 IS-IS SR IPv4 4 65 115 40

The cause is the PE's config, missing node-segment ipv4 configuration

PEa1.12:10:13#sh run int lo0

interface Loopback0

ip address 100.250.250.11/32

ipv6 address 2000:100:250:250::11/128

node-segment ipv6 index 11

isis enable MplsSR

isis passive

PEa1.12:25:24#c

PEa1.12:26:08(config)#int lo0

PEa1.12:26:10(config-if-Lo0)#node-segment ipv4 index 11

On RR1, NH emerges in tunnel rib.

RR1.12:22:56#show tunnel rib brief | grep 250.250.1

100.250.250.1/32 IS-IS SR IPv4 6 65 115 20

100.250.250.11/32 IS-IS SR IPv4 2 65 115 30

100.250.250.12/32 IS-IS SR IPv4 4 65 115 40

And bgp table is good

RR1.12:24:51#sh bgp evpn

BGP routing table information for VRF default

Router identifier 100.250.250.5, local AS number 65000

Route status codes: s - suppressed, * - valid, > - active, E - ECMP head, e - ECMP

S - Stale, c - Contributing to ECMP, b - backup

% - Pending BGP convergence

Origin codes: i - IGP, e - EGP, ? - incomplete

AS Path Attributes: Or-ID - Originator ID, C-LST - Cluster List, LL Nexthop - Link Local Nexthop

Network Next Hop Metric LocPref Weight Path

* > RD: 100.250.250.11:100 auto-discovery 110100 0000:0000:0000:0000:0000

100.250.250.11 - 100 0 i

* > RD: 100.250.250.12:100 auto-discovery 120100 0000:0000:0000:0000:0000

100.250.250.12 - 100 0 i

1/18/2021

Arista EOS: RSVP related features

References:

1/12/2021

Arista EOS: %ETH-4-ERRDISABLE: no-internal-vlan error detected

If you are seeing the following error message

Jan 12 19:03:19 sn452 Ebra: %ETH-4-ERRDISABLE: no-internal-vlan error detected on Ethernet81.

And the output of "show interface status" indicates some ethernet ports are error-disabled like

sn452.19:00:35(config-if-Et1-104)#show interfaces status errdisabled
Port Name Status Reason
----------- ---------------- ----------------- ----------------
Et81 errdisabled no-internal-vlan
Et82 errdisabled no-internal-vlan

The reason for the above error is that EOS running out of internal VLAN for routed ports. The EOS needs to assign an internal VLAN for the none switching ports. If you have the following 2 lines of configuration, you may hit this error

switchport default mode routed <<< all ports are routed
vlan internal order descending range 4001 4080 <<< but only 80 VLANs assigned

So the solution is to remove the internal VLAN range.

1/02/2021

Why unprotected ISIS segment routing prefix with TiLFA enabled

In the above topology, the output of "show isis segment-routing prefix" on PE11 shows the SID of PE22 is not protected.

bn303-PEa1.23:58:00(config-router-isis-af)#show isis segment-routing prefix-segments

System ID: 0000.0000.0011 Instance: 'isis-sr'

SR supported Data-plane: MPLS SR Router ID: 200.250.250.1

Node: 10 Proxy-Node: 0 Prefix: 0 Total Segments: 10

Flag Descriptions: R: Re-advertised, N: Node Segment, P: no-PHP

E: Explicit-NULL, V: Value, L: Local

Segment status codes: * - Self originated Prefix, L1 - level 1, L2 - level 2

Prefix SID Type Flags System ID Level Protection

------------------------- ----- ---------- ----------------------- --------------- ----- ----------

......

100.250.250.22/32 22 Node R:0 N:1 P:0 E:0 V:0 L:0 0000.0000.0022 L2 unprotected

100.255.255.31/32 31 Node R:0 N:1 P:0 E:0 V:0 L:0 0000.0000.0031 L2 node

The reason the SID of PE22 is "unprotected" is that the PE11 has a 2-way ECMP to the destination.

bn303-PEa1.23:58:01(config-router-isis-af)#show ip route 100.250.250.22/32

I L2 100.250.250.22/32 [115/50] via 100.2.11.0, Ethernet3/1/1

via 100.1.11.0, Ethernet10/36/1

Now let's the shutdown the interface between PE11 and P2 to break this ECMP. Now the prefix-segment is proteced now.

bn303-PEa1.00:14:21(config)#int e3/1/1

bn303-PEa1.00:14:27(config-if-Et3/1/1)#shu

bn303-PEa1.00:14:31#show ip route 100.250.250.22/32

I L2 100.250.250.22/32 [115/50] via 100.1.11.0, Ethernet10/36/1

bn303-PEa1.00:14:34#show isis segment-routing prefix-segments

Segment status codes: * - Self originated Prefix, L1 - level 1, L2 - level 2

Prefix SID Type Flags System ID Level Protection

------------------------- ----- ---------- ----------------------- --------------- ----- ----------

...

100.250.250.22/32 22 Node R:0 N:1 P:0 E:0 V:0 L:0 0000.0000.0022 L2 node

100.255.255.31/32 31 Node R:0 N:1 P:0 E:0 V:0 L:0 0000.0000.0031 L2 node

12/30/2020

Arista 7050CX - Packet Forwarding Pipeline

Reference: https://www.arista.com/assets/data/pdf/Whitepapers/Arista_7050X_Switch_Architecture.pdf

12/29/2020

Arista EOS: how to ping link local address under VRF

Here is the subinterface configuration:

interface Ethernet34.4007
description =>v7:Sp4-ck478
mtu 9214
encapsulation dot1q vlan 4007
vrf cust
ipv6 address fe80::1/64 link-local

To ping the remote link-local address, we could use

RtrA#ping vrf cust ipv6 fe80:: interface et34.4007
PING fe80::(fe80::) from fe80::1%et34.4007 et34.4007: 72 data bytes
80 bytes from fe80::1%et31.4007: icmp_seq=1 ttl=64 time=0.076 ms
80 bytes from fe80::1%et31.4007: icmp_seq=2 ttl=64 time=0.029 ms
80 bytes from fe80::1%et31.4007: icmp_seq=3 ttl=64 time=0.027 ms
80 bytes from fe80::1%et31.4007: icmp_seq=4 ttl=64 time=0.027 ms
80 bytes from fe80::1%et31.4007: icmp_seq=5 ttl=64 time=0.032 ms

12/02/2020

Arista EOS: % - Pending BGP convergence when "show bgp evpn"

1. Router(RR) receives 4 bgp evpn prefixes from RRC

wa465-PD.P1-JHM.SR.14:35:52(config-router-bgp-af)#show bgp evpn summary
BGP summary information for VRF default
Router identifier 100.250.250.30, local AS number 65000
Neighbor Status Codes: m - Under maintenance
Neighbor V AS MsgRcvd MsgSent InQ OutQ Up/Down State PfxRcd PfxAcc
100.250.250.11 4 65000 500 487 0 0 00:02:15 Estab 4 4
100.250.250.12 4 65000 504 488 0 0 00:02:15 Estab 4 4

2. But "show bgp evpn" complains about "Pending BGP convergence"

wa465-PD.P1-JHM.SR.14:36:48(config-router-bgp-af)#show bgp evpn

BGP routing table information for VRF default

Router identifier 100.250.250.30, local AS number 65000

Route status codes: s - suppressed, * - valid, > - active, E - ECMP head, e - ECMP

S - Stale, c - Contributing to ECMP, b - backup

% - Pending BGP convergence

Origin codes: i - IGP, e - EGP, ? - incomplete

AS Path Attributes: Or-ID - Originator ID, C-LST - Cluster List, LL Nexthop - Link Local Nexthop

Network Next Hop Metric LocPref Weight Path

% RD: 100.250.250.12:100 auto-discovery 0 0000:0000:0000:1111:0000

100.250.250.12 - 100 0 i

% RD: 100.250.250.12:1 auto-discovery 0000:0000:0000:1111:0000

100.250.250.12 - 100 0 i

3. Check the NH, it was resolved in the tunnel rib

wa465-PD.P1-JHM.SR.14:37:33(config-router-bgp-af)#show tunnel rib brief | grep 100.250.250.12

100.250.250.12/32 IS-IS SR IPv4 3 65 115 20

4. The cause is the mis-configuration under router bgp evpn address family. The EOS needs to know to resolve the NH by using the mpls NH tunnel rib.

wa465-PD.P1-JHM.SR.14:36:53(config-router-bgp-af)#router bgp 65000

wa465-PD.P1-JHM.SR.14:36:57(config-router-bgp)#add evpn

wa465-PD.P1-JHM.SR.14:37:00(config-router-bgp-af)#neighbor default encapsulation mpls next-hop-self source-interface loopback 0

wa465-PD.P1-JHM.SR.14:37:25(config-router-bgp-af)#show bgp evpn

BGP routing table information for VRF default

Router identifier 100.250.250.30, local AS number 65000

Route status codes: s - suppressed, * - valid, > - active, E - ECMP head, e - ECMP

S - Stale, c - Contributing to ECMP, b - backup

% - Pending BGP convergence

Origin codes: i - IGP, e - EGP, ? - incomplete

AS Path Attributes: Or-ID - Originator ID, C-LST - Cluster List, LL Nexthop - Link Local Nexthop

Network Next Hop Metric LocPref Weight Path

* > RD: 100.250.250.12:100 auto-discovery 0 0000:0000:0000:1111:0000

100.250.250.12 - 100 0 i

* > RD: 100.250.250.12:1 auto-discovery 0000:0000:0000:1111:0000

10/30/2020

BFD flaps in scale environment

In a lab scenario, says between 2 routers, there are hundreds of sub-interfaces and a BGP session with BFD on each subinterface. Then BFD flaps is seen. The scale information is as followed:

256 subinterfaces
256 ebgp session enabled with BFD
BFD timers are 50ms x 3

Addressing Type Up Init Down AdminDown

-------------------- -------------------- ------------- ----------- ----------- ---------

All All 239 [0] 8 [0] 9 [0] 0 [0]

IPv4 All 239 [0] 8 [0] 9 [0] 0 [0]

single hop All 239 [0] 8 [0] 9 [0] 0 [0]

normal 239 [0] 8 [0] 9 [0] 0 [0]

From the above output, you can see 17 of 256 sessions are not up. And HW BFD is enabled (by default in Eos), but no helps.

ghb289#show bfd hardware utilization
Chip Name Number Of HW Sessions* Maximum Number Of HW Sessions*
--------------- ---------------------------- ------------------------------
Jericho0 0 200
Jericho1 128 200
Jericho2 128 200

"show cpu counter queue" indicates high # of drop of CoppSystemBfd class, which means the receiving BFD packets exceeds the b/w limit of Copp.

ghb289#sh cpu counters queue |nz |grep -i bfd

CoppSystemBfd              Et16/2                5584344          390904080                  0                  0
CoppSystemBfd              Et51/2              783529888        57981211712            3985376          294917824

After increasing the shape/bandwidth of copp-system-bfd, there is bfd flaps anymore.

  Class-map: copp-system-bfd (match-any)
       shape : 25000 kbps
       bandwidth : 2500 kbps

9/30/2020

Arista EOS Lag/ECMP Hashing Features

References/Manual:

EOS Manual Section 12.4: Load Balancing Hash Algorithms

References/TOI:

Sample: In this below sample, I like to show how to use the above features to fix an ipv6 multicast unbalanced issue.

Says, in the above topology, there are 2000 ipv6 multicast streams flowing ixia-harness-[vrrp primary| secondary]-nexthop router. Let's see the output of srnz on VRRP primary.

1) w/o any hashing config, lowest vs highest = 220 vs 317

ghs259-GW2.21:24:15(config-if-Po2)#srnz | grep HUB

Et3/1 GW2-HUB2 0:05 0.0 0.0% 0 220.1 0.2% 35

Et4/1 GW2-HUB2 0:05 0.0 0.0% 0 316.9 0.3% 50

Et13/1 GW2-HUB2 0:05 0.0 0.0% 0 266.1 0.3% 42

Et14/1 GW2-HUB2 0:05 0.0 0.0% 0 269.3 0.3% 43

Po2 GW2-HUB2 0:05 0.0 0.0% 0 1072.3 0.3% 171

2) hash key shift

Let's try 1 hashing feature - Lag Hashing Key Shift. Create a LB profile - mcast-v6 + key shift, apply it globally.

ghs259-GW2.21:37:22(config)#load-balance policies

ghs259-GW2.21:37:28(config-load-balance-policies)# load-balance sand profile mcast-v6

ghs259-GW2.21:37:35(config-sand-load-balance-profile-mcast-v6)# ecmp hash key shift 3

ghs259-GW2.21:37:57(config)#port-channel load-balance sand profile mcast-v6

ghs259-GW2.21:39:50#srnz | grep HUB

Et3/1 GW2-HUB2 0:05 0.0 0.0% 0 220.1 0.2% 35

Et4/1 GW2-HUB2 0:05 0.0 0.0% 0 316.9 0.3% 50

...

Clearly, not much help.

3) hash seed

ghs259-GW2.21:42:47(config-load-balance-policies)#load-balance sand profile mcast-v6

! profile mcast-v6 is the current global profile

ghs259-GW2.21:42:52(config-sand-load-balance-profile-mcast-v6)#no ecmp hash key shift

ghs259-GW2.21:43:03(config-sand-load-balance-profile-mcast-v6)#ecmp hash seed 1001

ghs259-GW2.21:43:25(config-sand-load-balance-profile-mcast-v6)#end

ghs259-GW2.21:43:36#srnz | grep HUB

Et3/1 GW2-HUB2 0:05 0.0 0.0% 0 220.2 0.2% 35

Et4/1 GW2-HUB2 0:05 0.0 0.0% 0 316.9 0.3% 50

...

4) hash polynomial + Hardware load-balancing for ingress/egress and fabric/egress replication (4.18.0F)

ghs259-GW2.21:45:26(config)#load-balance policies

ghs259-GW2.21:45:30(config-load-balance-policies)#load-balance sand profile mcast-v6

! profile mcast-v6 is the current global profile

ghs259-GW2.21:45:35(config-sand-load-balance-profile-mcast-v6)#no ecmp hash seed 1001

ghs259-GW2.21:45:42(config-sand-load-balance-profile-mcast-v6)#port-channel hash polynomial 5

ghs259-GW2.21:45:43(config-load-balance-policies)# port-channel load-balance sand replication egress

ghs259-GW2.21:46:52#srnz | grep HUB

Et3/1 GW2-HUB2 0:05 0.0 0.0% 0 265.3 0.3% 42

Et4/1 GW2-HUB2 0:05 0.0 0.0% 0 272.3 0.3% 43

Nice! The hash polynomial works! Actually EOS 8 polynomial functions, the #5 works.

9/23/2020

Understanding the output of "show qos interface eth#"

In this post, I like to explain the output of the EOS command - "show qos interface eth#" based on my understanding from EOS document.

wa461.00:58:25#sh qos interfaces e17/1
Ethernet17/1:
Trust Mode: DSCP
Default COS: 0
Default DSCP: 0

Port shaping rate: disabled
Burst-size: disabled

Tx Bandwidth Shape Rate Burst-Size Priority ECN/WRED
Queue (percent) (units) (units)
------------------------------------------------------------------------------------------
7 - / - - / - ( - ) - / - SP / SP D
6 - / - - / - ( - ) - / - SP / SP D
5 - / - - / - ( - ) - / - SP / SP D
4 - / - - / - ( - ) - / - SP / SP D
3 - / - - / - ( - ) - / - SP / SP D
2 20 / 20 1.2 / 1.0 (Gbps) 2048 KB / 2048 KB RR / RR D
1 30 / 30 - / - ( - ) - / - RR / SP D
0 50 / 50 - / - ( - ) - / - RR / SP D

Note: Values are displayed as Operational/Configured
Legend:
RR -> Round Robin
SP -> Strict Priority
- -> Not Applicable / Not Configured
% -> Percentage of line rate

Values are displayed as Operational/Configured, like RR/SP which means this Q is configured as strict priority but operational as round-robin.
If one queue is configured as no priority (RR), then all the lower queues are changed to RR.

In this example, Q 2 is RR, then 0 and 1 are automatically changed to RR.
And Q 0 and 1 are RR/SP, which means their configuration are SP by default, but operational mode is RR.

If both interface and tx-queue are configured with shape, which is effective?

From EOS manual chapter 27.5 - Enabling port shaping on an FM6000 interface disables queue shaping internally. Disabling port shaping restores queue shaping as specified in running-config.

interface Ethernet17/1
speed forced 10000full
!
tx-queue 0
bandwidth percent 50
!
tx-queue 1
bandwidth percent 30
!
tx-queue 2
no priority
bandwidth percent 20
shape rate 1000000

Bandwidth vs shape.

Bandwidth% is the b/w percent this RR queue can get. Says the above configuration:

In the sample below, the interface 17/1 is 10 Gbps interface
Q3-7 are the strict priority and, say use total 2 Gbps traffic, which left 8Gbps for Q0-2
The tx-Q 2 can have 20% of left-over capacity which is 1.6Gbps
But the shape rate is 1.2Gbps
So the maximum throughput of tx-Q 2 is 1.2 Gbps, even it is assigned with 1.6Gbps.

EOS: A simple Qos design example

This article - "A Simple Quality of Service Design Example" is a very good starting point for understanding the EOS Qos architecture and starting a Qos design.

Some points:

3 ways in the ingress points to map packets to Tx queues:

qos cos trust + cos-tc map
qos dscp trust + dscp-tc map
service-policy + policy-map

3 big categories of traffic:

network-control = control plane
latency/jitter sensitive traffic
best-efforts = scavenger traffic

qos profile =

policy-map for input
tx-queue set for output

"no priority" in a tx-queue, all lower queues become RR

9/22/2020

Support for CPU traffic policy

The default EOS Copp only provides protocol level traffic policy, for example, the maximum throughput of bgp traffic destined to the cpu. But there is no granularity of source address. So this feature - Support for CPU traffic policy is for this purpose.

Set DSCP value for CPU outbound packets

In Arista EOS, the following protocol packets are able to set a DSCP value other than the default value 0:

Notes:

The setting must be done individually and under the protocol section
hostname is not supported.

For example, setting all locally originated CP packets to DSCP value nc1/cs6/110000/63:

logging qos dscp 48

dns qos dscp 48

ntp qos dscp 48

traceroute qos dscp 48

sflow qos dscp 48

！

snmp-server qos dscp 48

！

radius-server qos dscp 48

！

tacacs-server qos dscp 48

！

management ssh

qos dscp 48

router ospf general

qos dscp 48

9/13/2020

EOS: % Not supported when show bgp summary

If you see the error message with EOS command - show bgp <AF> summary, it is probably caused the routing mode. To be more specific, you are probably running ribd mode and the CLI - "show bgp <AF> summary" is only supported in multi-agent mode

ghs259#show bgp ipv6 unicast summary
% Not supported

ghs259-CIN-DPA2.23:32:18#show ip route summary
Operating routing protocol model: ribd
Configured routing protocol model: multi-agent (will apply after next reboot)

8/19/2020

Arista EOS - BGP Selective Route Download

In this post, I will share my experience with a relatively old (was released back in 2015) but very useful Arista EOS feature - BGP Selective Route Download (SRD).

The use cases are quite straightforward:

Program the necessary routes on the routers with small hardware resources. In the above TOI link, only 30K prefixes of 520K (back in 2015) cover 99% traffic. The left small traffic can be directed by the default route.
Another useful case (for me) is to control what routes be programmed, or even not installed at all. At meanwhile the BGP runs transparently, which processes, receives and advertises the BGP prefixes. A good example is the RR which is not in the data path. Or hardness router in the lab, it just sends bgp updates. The traffic can be handled by a couple of static routes.

In the below example, BGP only installs /24 IPv4 routes within 110.0.0/8 range and /64 IPv6 routes in 2000:110:1::/48.

router bgp 65501

bgp route install-map part-peer-v46

route-map part-peer-v46 permit 10

match ip address prefix-list part-peer-route

route-map part-peer-v46 permit 20

match ipv6 address prefix-list part-peer-route-v6

ip prefix-list part-peer-route seq 10 permit 110.0.0.0/8 eq 24

ipv6 prefix-list part-peer-route-v6

seq 10 permit 2000:110:1::/48 eq 64

bn309#show ip route summary

...

VRF: default

Route Source Number Of Routes

------------------------------------- -------------------------

...

ospfv3 0

bgp 1814

External: 1814 Internal: 0

...

Total Routes 1871

Number of routes per mask-length:

/8: 2 /12: 2 /16: 1 /24: 1816 /25: 1

/30: 7 /32: 42

bn309#show ip bgp installed | egrep '^ \* ' | wc -l

1816

At this time actually, this router receives/accepts over 1.4M prefixes.

bn309#show ip bgp summary

BGP summary information for VRF default

Router identifier 192.168.230.2, local AS number 65501

Neighbor Status Codes: m - Under maintenance

Description Neighbor V AS MsgRcvd MsgSent InQ OutQ Up/Down State PfxRcd PfxAcc

IpTransit#1-7504 100.101.1.1 4 12083 44303 119708 0 0 01:08:12 Estab 690049 690049

Local-Aris-Simu 192.168.230.1 4 65510 129394 5 0 0 01:03:57 Estab 819857 819857

As of August 2020, this feature is only supported on RIBD (so multi-agent mode doesn't work)

8/10/2020

EOS: alias to sum up total num of received bgp prefixes

EOS-R1#show ip bgp neighbors

BGP neighbor is 100.101.1.2, remote AS 100, external link

Prefix Statistics:

Sent Rcvd Best Paths Best ECMP Paths

IPv4 Unicast: 688000 818876 808929 0

IPv6 Unicast: 0 0 0 0

If we like to know the total number of rcvd prefix from all bgp peers, here is the alias command could be useful

alias totbgp show ip bgp neighbors | grep "IPv4 Unicast: \s\s" | awk '{s+=$4}END{print s}'

EOS-R1#totbgp

6001256

7/27/2020

EOS: sum up and compare in/egress throughput

Sometimes you want to compare the ingress/egress throughput on a particular router to see if any possible traffic loss (of course, the loss should be large enough like 3% more). On EOS, srnz (alias srnz Show interface counters rates | nz) is a good alias. But if incoming or outgoing on multiple ports, you have to sum up and compare.

Here is a couple of useful tips and commands.

bn309#srnz
Port Name Intvl In Mbps % In Kpps Out Mbps % Out Kpps
Et9/1/1 ixia:LC8 0:05 0.0 0.0% 0 13435.8 35.0% 3543
Et9/2/1 ixia:LC8 0:05 0.0 0.0% 0 13435.3 35.0% 3543
...
Et11/6/1 ixia:LC7 0:05 13433.7 35.0% 3543 0.0 0.0% 0
Et11/11/1 ixia:LC7 0:05 13433.7 35.0% 3543 0.0 0.0% 0
Et11/12/1 ixia:LC7 0:05 13434.6 35.0% 3543 0.0 0.0% 0
Et11/13/1 ixia:LC7 0:05 13432.3 35.0% 3543 0.0 0.0% 0
Et11/14/1 ixia:LC7 0:05 13434.4 35.0% 3543 0.0 0.0% 0
Et11/15/1 ixia:LC7 0:05 13434.3 35.0% 3543 0.0 0.0% 0
Et11/16/1 ixia:LC7 0:05 13433.9 35.0% 3543 0.0 0.0% 0

In the above example, you want to compare ingress from ixia:LC7 and egress of ixia:LC8

bn309#srnz | grep LC7 | awk '{s+=$4}END{print s}'
161206 <<< ingress
bn309#srnz | grep LC8 | awk '{s+=$7}END{print s}'
161198 <<< egress

6/30/2020

"no-internal-vlan" error for routed interfaces

Creating several L3 routed port-channels and sub-interfaces, but they failed to come up with errdisabled status. The output "show interface status err" displays the following reasons:

yo411.16:22:08(config-if-Po1201)#show int status errdisabled
Port Name Status Reason
-------------- ---------------- ----------------- ---------------------
Et3/12/1 errdisabled port-channel-shutdown
Et4/12/1 errdisabled port-channel-shutdown
Po1201.3 errdisabled no-internal-vlan
Po1201.2 errdisabled no-internal-vlan
Po1201 errdisabled no-internal-vlan

Basically, the "port-ch-shutdown" error was caused by the Po1201 being down. Checked the EOS document, the system will reserve an internal VLAN for any "no switchport" interfaces. And the internal VLAN ranges start from 1006 to 4094 (ref: EOS Manual section 19.4.3)

yo411.16:22:59(config-if-Po1201)#show vlan internal usage
1006 Port-Channel1900.4002
1007 Ethernet3/36/3
1008 Port-Channel1900
1009 Ethernet3/36/1
1010 Port-Channel1900.4003
1011 Ethernet3/36/4
1012 Ethernet3/36/2
1013 Ethernet3/36/4.2
1014 Ethernet3/36/4.3

And internal VLAN assignment stops at 1015.

yo411.16:23:23(config-if-Po1201)#sh vlan 1015
VLAN Name Status Ports
----- -------------------------------- --------- -------------------------------
1015 VLAN1015 suspended

So the root cause is that there is an accidental configuration of vlan 1015 with a suspended state, and this blocks the internal VLAN assignment.

yo411.16:24:19(config)#no vlan 1006 - 1099
yo411.16:24:36(config)#sh int status errdisabled

After removing the VLAN configuration, there is no internal-VLAN error anymore.

yo411.16:24:47(config)#show vlan internal usage
...
1015 Port-Channel1201.2
1016 Port-Channel1201.3
1017 Port-Channel1201

Another way is to specify the internal VLAN range to an unused space (ref: EOS manual section 21.3)

yo411(config)# vlan internal order descending range 4000 4094