Arista J/J+ FlexRoute with Internet Routing Table

https://www.arista.com/assets/data/pdf/Whitepapers/FlexRoute-WP.pdf

• CLI: 
• ip hardware fib optimize prefix-length internet
• show ip bgp summary
• show ip route summary
• show hardware capacity | grep Routing
• Routing HW resources are sliced to fit the route distribution of REAL internet routing table
• If loading a lab configuration like Ixia, you mean see the error message like - "%CAPACITY-1-UTILIZATION_HIGH. LEM table utilization is currently at 91%, crossed threshold 90%"
• For example, if too many /24, it will be moved to LEM
• And another important concept of prefix, route and FIB:
• 3 x internet feeds = 3 x 600K prefixes
• 3 prefixes of same dest = 1 route with 3 NH if ECMP
• 1 route = 1 FIB entry

IP fragmentation on Arad platform

• Fragmented/MTU violated packet is sw forwarded and shaped by CoPP or PDP;
• CoPP = 2~2.5 Mbps
• "no shape" under copp-system-mtu can make it 100Mbps
• PDP = 100 Mbps
• But not a good idea to do it. 

TH/Trident low LPM

On Arista DCS-7260CX-64-F platform, if you see hw resource - LPM/V4Routes running out, have to change the "platform trident forward partition". Agent will restart but doesn't a reboot. 

nv475.08:45:07(config)#sh hardware capacity utilization percent exceed 50
Forwarding Resources Usage

Table   Feature    Chip       Used   Used      Free    Committed    Best Case        High
                           Entries    (%)   Entries      Entries          Max   Watermark
                                                                      Entries
------- ---------- ------ --------- ------ ---------- ------------ ------------ ---------
LPM                           8190   100%         0            0         8190        8190
LPM     V4Routes              8190   100%         0            0         8190        8190

nv475.08:52:45(config)#sh ip route 151.131.34.0

VRF: default
======================================================
WARNING: Some of the routes are not programmed in
hardware, and they are marked with '*'.
======================================================

*B E    151.131.34.0/24 [200/0] via 100.1.0.44, Vlan10

nv476.11:05:47#sh platform trident forwarding-table partition

L2 Table Size: 72k

L3 Host Table Size: 72k

LPM Table Size: 16k, uRPF is disabled

nv475.09:27:35(config)#platform trident forwarding-table partition ?

  0  136k l2 entries, 8k l3 host, 16k lpm entries

  1  104k l2 entries, 40k l3 host, 16k lpm entries

  2  72k l2 entries, 72k l3 host, 16k lpm entries

  3  40k l2 entries, 104k l3 host, 16k lpm entries

  4  8k l2 entries, 8k l3 host, 90k lpm entries <<< this one!

But this change will impact MLAG because lower MAC capacity. 

Take away notes from RFC5549 video by AMX-IX

• https://www.youtube.com/watch?v=uJOtfiHDCMw
• AMS-IX running out /22 ipv4 NH address space
• Solution #1: more address space:
• ARP broadcast too much
• Solution #2: private address by RFC1918, 10/8, 172.16/12, 192.168/16
• Space used by ISP customer
• More specific in IGP
• Break traceroute
• Solution #5: RFC5549
• IPv4 NLRI over IPv6 NH
• 2 ways to implement it:
• v4 in v6 tunnel, add 40B head
• direct forwarding - just replace the MAC, no change;