VLAN issues on ASR1004

[DirkDietz5932]

Hi all,

we are having trouble with VLAN tagging with 1G interfaces on ASR1004.

Here the interface config:

interface GigabitEthernet0/0/7.102
 encapsulation dot1Q 137
 ip address 2.32.99.81 255.255.255.252

When pinging the next hop it fails:

Router#do ping 2.32.99.82
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2.32.99.82, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
Router#

We tested a lot but found one solution so far and changing the interface name only:

Router#conf t
Router(config)#no int GigabitEthernet0/0/7.102               ! deleteing old interface
Router(config)#int GigabitEthernet0/0/7.10200000             ! creating new interface
Router(config-subif)#encapsulation dot1Q 137                 ! same encapsulation id
Router(config-subif)#ip address 2.32.99.81 255.255.255.252   ! same ip address

When pinging the next hop it works:

Router#ping 2.32.99.82
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2.32.99.82, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 2/7/28 ms
Router#

Does anybody has an idea what this could be? It's just another interface naming, encapsulation is the same. This happens more and more and is "destroying" the interface naming structure we use.

Thanks a lot to you

Bye

Dirk

[paul driver]

Hello

It shouldn't matter if the sub-interface number is different to the vlan id  as you have shown but it is best practice to have them both the same.

In the past i have found a reload of the device is required to fully clear ghost sub-interface entries, have you tried this and tested again?

[DirkDietz5932]

Hi Paul,

thanks for your feedback but the issue I have is not what you are talking about.

The issue I have is that any interface with dedicated VLAN id does not work. When deleting this interface and creating a new one with absolut same VLAN id it works again.

Please have close look on my config and ping result. A reboot does not solve the issue.

Many thanks

Dirk

[Richard Burts]

I think that @paul driver raises an interesting point about the possibility of ghost interfaces. Would you post the output of show ip interface brief?

HTH

Rick

[DirkDietz5932]

Hi Rick,

the interface is already in deleted status.

Gi0/0/7.102            unassigned      YES manual deleted               down     

Yes something like ghost interfaces sounds magic as the config itself is the same compared to the working subinterface.

Thanks

Dirk

[Richard Burts]

Dirk

There may be more than one issue in this discussion. One issue is about "ghost" subinterfaces which have been deleted from the config but still show up in the output of show ip interface brief (and which can present challenges if you attempt to change certain aspects of their configuration). My experience has been that the only way to get these ghost sub interfaces to really go away has been to save the config and reboot.

But it appears that your original issue was probably not really about ghost subintefaces. You report that a subinterface is configured, that ping through that subinterface fails, and that configuring a new subinterface with the same vlan tagging does work. We need to do some additional investigation about this issue. The next time that it happens please provide the output to these commands:

show ip interface brief

show interface <interface_id>

show arp

HTH

Rick