ASR903 RSP3_400 GRE tunnel Support

[Alireza Soltanian]

Hi

Recently, we got a ASR 903 RSP3_400. We are doing some tests on it. One of them is passing traffic over GRE tunnel. This test was failed. Here is the brief description of scenario:

PC1----ASR----GRE----C7200---PC2

ASR and C7200 are OSPF neighbors over GRE tunnel. Ping from PC2 to PC1 and vice versa fails.

After several investigation and packet capture, I found out ICMP echo request from PC2 is received by PC1 and PC1 sends a reply but this replay packet is not placed on GRE tunnel by ASR while the request is passed over GRE tunnel.

I had an experience with ASR920 which it did not support GRE tunnel encapsulation/de-encasulation. I wonder is this applicable for the is model of ASR Series or not.

This is the configuration of Interfaces on ASR:

interface Tunnel1800
 description ASR-TUNNEL-to-BRAS
 ip address 70.70.70.2 255.255.255.252
 ip mtu 1470
 ip ospf mtu-ignore
 ip ospf cost 100
 load-interval 30
 tunnel source 10.199.4.222
 tunnel destination 10.199.5.107
 tunnel checksum

!

interface GigabitEthernet0/0/1

 description Toward_PC1
 no ip address
 load-interval 30
 negotiation auto
 cdp enable
 service instance 1801 ethernet
  encapsulation dot1q 1801
  rewrite ingress tag pop 1 symmetric
  bridge-domain 1801

!

interface BDI1801
 ip address 4.4.4.1 255.255.255.0

!

This is the IOS-XE version:

Cisco IOS XE Software, Version 03.18.01.S - Extended Support Release
Cisco IOS Software, ASR900 Software (PPC_LINUX_IOSD-UNIVERSALK9_NPE-M), Version 15.6(2)S1, RELEASE SOFTWARE (fc1)

Can you please help me in this regard?

Thank you

Alireza

[Philip D'Ath]

I don't know what the problem is.  I am suspicious of "tunnel checksum".  Could you try removing that from both ends?

Can the two routers ping each other over the tunnel?

Has an OSPF neighbour adjacency been formed over the tunnel?

I noticed you have used "ip ospf mtu-ignore".  You should make the tunnel MTUs the same on both ends rather than doing this.

[Alireza Soltanian]

Dear Philip

I removed "tunnel checksum" and there was no luck.

Yes they form OSPF neighbor adjacency and both side of Tunnel can be ping from the other side.

Having or not having MTU-Ignore does not solve the case.

I wonder Does ASR902 have required data plane for GRE tunnel? Did you work with this model? and if the answer is yes did you have GRE tunnel on this platform?

Thank you

[Alireza Soltanian]

I think the issue is related to encapsulation of packets on ASR903 while it is received on Gig0/0/1.

The packet is de-encapsulated when it is received from GRE and it is sent to Gig0/0/1. I can see this in Wireshark output on PC1.

PC1 sends the reply but the Reply packet is not encapsulated in GRE headers by ASR903.

Does anybody have any clue?