Can't ping thru 7604 subinterface...

Unanswered Question
Nov 13th, 2007
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I have a 7604 with a SIP-400 and a SPA-2GE. On one of the GE ports I have this config:


int g2/0/1.50

encap dot1q 50

ip address 192.168.10.1 255.255.255.128


router eigrp 1

network 192.168.10.0


It is connected to a L2 3750 port with this config:


int g0/1

switchport

switchport mode access

switchport access vlan 50


int vlan 50

ip address 192.168.10.2 255.255.255.128


ip default-gateway 192.168.10.1


On the 7604 I can ping 192.168.10.1 but not the 3750 192.168.10.2. On the 3750 I can ping 192.168.10.2 but not the 7604 192.168.10.1.


If I get rid of the 7604 sub-interface and config the main interface like:


int g2/0/1

ip address 192.168.10.1 255.255.255.128


...I can ping both IP addresses from both devices.


Is there a problem with sub-interfaces on the 7604? It seems like the sub-interface dot1q 50 is not matching up with the 3750 vlan 50. I know I'm missing something simple.

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Richard Burts Tue, 11/13/2007 - 13:26
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Jim


There is not a problem with subinterfaces on 7604 as long as you use them in consistent ways. But you are trying to use them in inconsistent ways. When you configure the subinterface on the 7604 you are setting it up to process as a trunk. But on the switch you have configured the port as an access port and not as a trunk port.


Your point is well taken that It seems like the sub-interface dot1q 50 is not matching up with the 3750 vlan 50. It is not matching because one end is trying to trunk and the other end is trying to access.


You resolve this difficulty either by configuring the interface on the 7604 as access not trunk (by removing the subinterface and configuring on the physical interface) or you fix it by configuring the interface on the switch as a trunk port.


HTH


Rick

jkeeffe Tue, 11/13/2007 - 13:39
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I knew it was a simple solution - like having the name of a location on the tip of my tongue but just can't quite remember it. Thanks!

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