06-20-2018 02:11 AM - edited 03-08-2019 03:25 PM
I am facing an odd layer 2 behavior between 4 Cisco Router ASR1002-HX connected at the same Cisco Catalyst 2960 within the same vlan. Randomly each router can't reach the others within the same local vlan.
No layer 1 issues are present.
We face the same issue trying change L2 switch, sfp, cables, vlan, ip addresses, removing any L3 protocol and static route, clearing arp and setting static arp entries.
Updating the firmware from 16.3.3 to 16.3.6 did not solve.
Did someone ever face the same issue?
06-20-2018 02:36 AM
What is the issue? Do you have a ping loss? how many pings? How many times? It's jus a ping or the routers are unreachable for minutes?
Regards.
06-20-2018 02:59 AM
The issue is related to any type of traffic. Sometimes ping works, sometimes not. Furthermore iBGP sessions flap.
06-20-2018 03:02 AM
Is it a flap of 1 second or the duration is higher?
06-20-2018 05:03 AM
iBGP sessions survive for about 1 minutes then restart because of the lack of connectivity.
06-20-2018 05:17 AM
During the issue, can you see the mac-address of the routers on the switch?
Regards.
06-20-2018 06:17 AM
Yes, I can see the mac-address.
Probably I've found the mistake but I've got no idea how to fix it.
Routers interfaces that have that issue have an ip addresses within the 192.168.0.0/22 network.
I'm announcing that /22 prefix to some eBGP peers, but I would like also to announce 192.168.0.0/24.
To reach that goal I have configured a static ip route /24 out of that same network.
If I delete that static route everything seems to working fine, but the /24 is not announced to bgp peers because it is not within the routing table.
How can avoid this behavior?
06-20-2018 06:19 AM
Try this trick:
ip route 192.168.0.0 255.255.255.0 null0
Let me know what happens.
Regards.
06-20-2018 06:26 AM
Same behavior because the network is matched at the same way.
ip route 192.168.0.0 255.255.255.0 GigabitEthernet0/0/0
Has the same result of
ip route 192.168.0.0 255.255.255.0 null0
06-20-2018 06:48 AM
mmm, you must have a route installed in your global routing table in order to announce it...
what is the pourpose of this route?
06-21-2018 12:21 AM
I'm trying to announce the aggregate /22 and the 4 more specific network /24 from each of the 4 routers.
Each router has an ip address of the /22 and the subnet mask /22.
06-21-2018 07:05 AM
06-22-2018 12:52 AM
07-24-2018 07:41 AM
I'm not sure about the answer to that question.
I would suggest performing a long duration ping and make note of the intervals of when it responds and when it does not. Perform it from each of the routers to see if they stop at the same time. That can provide clues to what the source of the problem is.
Prior to starting those pings check to see if you already have an ARP entry.
Do those routers go to a single switch?
07-24-2018 08:49 AM
I believe that checking for arp entries is a good place to start. It would also be helpful if the original poster can provide some details of how these routers are connected and the details of the configuration of the router interfaces.
HTH
Rick
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