Cisco 3945 question

Hi everyone,

I have a Cisco 3945 with a 3560 switch card. The switch card has 16 ports, plus 2 ports, g0/17 and g0/18 for what I thought was the layer 2 and 3 connections to the router. It was my understanding that g0/17 was used for trunking vlans to the sub interfaces on the router, and the g0/18 was used for layer 3 connection (I had an IP assigned in the same subnet as the g1/0 interface on the router so I could use ssh to connect to the switch card vice using the command "service-module g1/0 session").
However, during testing I noticed that if I trunked g0/17 I was unable to ping from an interface on the switch card to a sub interface on the router (same subnets), while I could with the same trunking configuration on g0/18. Of course this requires me to remove the ip address I use for ssh from g0/18. I also tried assigning the IP to g0/17 but was unable to ping from the g1/0 interface on the router to the g0/17 IP on the switch card.

Does anyone have experience with this that could explain the concept of those two ports on the switch card?

Answers

  • Well I did actually get it to work by adding an svi on the switch card for a management vlan, adding that vlan to g0/18 trunk, and adding a sub interface on the router for management in the same subnet as on the switch card. This enables me to use ssh only and trunk everything over g0/18.

    Would still like to know the purpose of g0/17 though, if anyone has experience with this.

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