Problems with VLANs between cisco 7200 routers

Unanswered Question
Oct 10th, 2008
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I have a point to point link between 2 Cisco 7200s that I'm being

required to add VLAN tagging to.

Here are the interface configs:

Router A:

interface FastEthernet5/0

no ip address

duplex full


interface FastEthernet5/0.253

encapsulation dot1Q 253

ip address

Router B:

interface FastEthernet4/0

no ip address

duplex full


interface FastEthernet4/0.253

encapsulation dot1Q 253

ip address

However, when AT&T forces tagging on the ports, I cannot ping from .

249 to .250, and AT&T cannot see my MAC address on their switches

inbetween and zero traffic on the VLAN.

Does anyone have any ideas?

Router A is a 7206VXR running 12.2(4r)

Router B is a 7204VXR running 12.2(12a)

Thank you.

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Jon Marshall Fri, 10/10/2008 - 01:04
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Can you check with your provider

1) That they have configured the link as 802.1q trunk

2) That vlan 253 exists on their switch infrastructure


jlamanna1 Fri, 10/10/2008 - 06:16
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I know they have configured the link as 802.1q on vlan 253.

svanguilder Sat, 10/11/2008 - 05:07
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I had a similar issue on a couple of our routers they are 2811s, but probably a similar situation. I had to to VLAN tagging for a different reason, but had similar results. What I wound up doing was to remove the IP address from the subinterface and put on apply to the parent interface. Here is a snippet from the config.


interface FastEthernet0/1

ip address xx.xx.245.65

duplex auto

speed auto


interface FastEthernet0/1.1

description $ETH-LAN$

encapsulation dot1Q 20

no snmp trap link-status


Once I did that it worked fine.

The HQ end was different because of the hardware we used.


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