Arista EOS Tunneling Mechanism (3) - Sw Tunnel + ISIS

 

Above is a simple setup to demonstrate the feature of ISIS over GRE tunnel. It is worthy to note that:

• This tunnel is a software tunnel without hardware programming. It ONLY works for the local packets generated by CPU and is capped by CoPP policy. So no data/traffic traffic is thru the tunnel. 
• The only valid use case per TOI is to advertise the ISIS routes to a remote application, like below
• The application can learn the whole view of a network topology
• Based application or business intelligence, it can program the routers to instruct the traffic flows. So a practical SDN solution to me. 

Limitation:

• IPv6 underlay endpoint is not supported
• Underlay VRF is not supported
• That says the tunnel source/destination must be ipv4 address under default VRF.

Some extras:

• Even in the above the TOI, it says it only supports ISIS, but in the lab, the BGP session is up and running w/o any issue. But one thing to be aware is to assign the tunnel interface TTL. Otherwise, the neighbor fails to come up

R11(config-router-bgp)#sh run sec router bgp

router bgp 11

   neighbor 10.100.100.44 remote-as 44

   neighbor 10.100.100.44 maximum-routes 12000

   redistribute connected

R11(config-router-bgp)#sh ip bgp sum

BGP summary information for VRF default

Router identifier 11.11.11.11, local AS number 11

Neighbor Status Codes: m - Under maintenance

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

  10.100.100.44    4  44              4002      4013    0    0 01:29:18 Estab   11     11 <<<< session is up

• Overlay VRF is supported, so tunnel interface can belong to none-default VRF

R11(config)#sh run int tunnel 101

interface Tunnel101

   description sw-tunnel-gre-vrf-v1

   vrf forwarding v1

   ip address 10.101.101.11/24

   isis enable isis.over.GRE.v1

   isis bfd

   isis network point-to-point

   tunnel mode gre

   tunnel source 11.11.11.1

   tunnel destination 44.44.44.1

R11(config)#sh int tunnel 101

Tunnel101 is up, line protocol is up (connected)

  Hardware is Tunnel, address is 0b0b.0b01.0800

  Description: sw-tunnel-gre-vrf-v1

  Internet address is 10.101.101.11/24

  Broadcast address is 255.255.255.255

  Tunnel source 11.11.11.1, destination 44.44.44.1

....

R44(config)#sh run int tu101

interface Tunnel101

   description sw-tunnel-gre-vrf-v1

   vrf forwarding v1

   ip address 10.101.101.44/24

   isis enable isis.over.GRE.v1

   isis bfd

   isis network point-to-point

   tunnel mode gre

   tunnel source 44.44.44.1

   tunnel destination 11.11.11.1

R44(config)#sh int tu101

Tunnel101 is up, line protocol is up (connected)

  Hardware is Tunnel, address is 2c2c.2c01.0800

  Description: sw-tunnel-gre-vrf-v1

  Internet address is 10.101.101.44/24

  Broadcast address is 255.255.255.255

....

R11(config)#ping vrf v1 10.101.101.44

PING 10.101.101.44 (10.101.101.44) 72(100) bytes of data.

80 bytes from 10.101.101.44: icmp_seq=1 ttl=64 time=0.234 ms

80 bytes from 10.101.101.44: icmp_seq=2 ttl=64 time=0.153 ms

...

R11(config)#sh isis neighbors vrf v1

Instance  VRF      System Id        Type Interface          SNPA              State Hold time   Circuit Id

isis.over v1       R44              L1   Tunnel101          P2P               UP    25          87

R11(config)#sh ip route vrf v1 isis

VRF: v1

....

 I L1     101.101.44.1/32 [115/11] via 10.101.101.44, Tunnel101

 I L1     101.101.44.2/32 [115/11] via 10.101.101.44, Tunnel101

 I L1     101.101.44.3/32 [115/11] via 10.101.101.44, Tunnel101

 I L1     101.101.44.4/32 [115/11] via 10.101.101.44, Tunnel101