Posted on August 18, 2020 3:22 am
 |  Asked by Duc Le
 |  89 views
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Hi,

We are configuring L3 VPN service using EVPN route type 5. I can see the route in the bgp table of the VRF but in the route table, the destination of the learned prefix is null0. Can someone explain why and how to fix it? I am running vEOS 4.24.0F in our lab.

Here is the output of the bgp table in the VRF:

AT1-R1#show ip bgp 10.37.4.0/23 vrf CORE
BGP routing table information for VRF CORE
Router identifier 10.32.25.2, local AS number 65032
BGP routing table entry for 10.37.4.0/23
Paths: 1 available
65037 65370
2.2.2.3 from 1.1.1.103 (2.2.2.3), imported EVPN route, RD 1.1.1.103:50001
Origin IGP, metric 0, localpref 100, IGP metric 0, weight 0, received 00:08:29 ago, valid, external, best
Extended Community: Route-Target-AS:50001:50001 TunnelEncap:tunnelTypeVxlan EvpnRouterMac:50:01:00:27:03:91
Remote VNI: 50001
Rx SAFI: Unicast

Here is the output of the route table in the vrf:

AT1-R1#show ip route vrf CORE

VRF: CORE
Codes: C – connected, S – static, K – kernel,
O – OSPF, IA – OSPF inter area, E1 – OSPF external type 1,
E2 – OSPF external type 2, N1 – OSPF NSSA external type 1,
N2 – OSPF NSSA external type2, B – BGP, B I – iBGP, B E – eBGP,
R – RIP, I L1 – IS-IS level 1, I L2 – IS-IS level 2,
O3 – OSPFv3, A B – BGP Aggregate, A O – OSPF Summary,
NG – Nexthop Group Static Route, V – VXLAN Control Service,
DH – DHCP client installed default route, M – Martian,
DP – Dynamic Policy Route, L – VRF Leaked,
RC – Route Cache Route

Gateway of last resort is not set

B E 10.32.4.0/23 [20/0]
via 10.32.25.1, Ethernet5
C 10.32.25.0/30 [0/0]
via Ethernet5, directly connected
B E 10.37.4.0/23 [20/0]
Null0

You can see that the prefix 10.37.4.0/23 is already imported to the bgp table within the VRF but the route table show destination of Null0 instead the remote VTEP ip address.

Thanks alot

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Posted by Aniket Bhowmick
Answered on August 18, 2020 7:27 am

Hi Duc

Thanks for reaching out !

Do you mind sharing the output of the following command: "show ip route 2.2.2.2"

Additionally, if  you can attach the output of "show tech-support | no", it will be very helpful as it will give all necessary information we need to investigate this.

Thanks,

Aniket

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Answered on August 18, 2020 8:25 am

Hi Duc,

Thank you for contacting Arista.

Could you please provide us the topology diagram explaining the flow of traffic.

In addition to the above outputs could you please provide us the below logs:

show tech-support bgp  | no

show tech extended evpn | no

We are suspecting the possibility of routing loop here and the above logs would help in investigating the same.

Thanks,

Bhavana.

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