Some Questions on VLAN Trunking and Layer 3 Routing

Sep 19, 2008 1 Replies

Hope this is not to verbose.


-- What I am trying to do:



I am trying to configure a Cisco 2948G-L3 and a Cisco 3548 for vlan trunking. I am



currently using the Cisco 2948G-L3 as a router. It is not configured with VLANs, it has



various groups of ports configured in seven different BVIs. Each BVI has an ip assigned



and acts as the default gateway for end stations on its respective subnet. This all



works great and we have used it for years.



I am now trying to figure out how to configure the Cisco 2948G-L3 to terminate a VLAN



trunk from a Nortel switch that we will be getting soon for some wireless phones. We



will also be using the Nortel wireless network for a few wireless workstations and



laptops. We will have four VLANs on the Nortel switch. Two of them do not need to trunk



to the Cisco 2948G-L3 as they will have ports on the Nortel switch assigned to them to



get to devices.



I also thought I would create and additional BVI, Bridge-group 111 on the Cisco 2948G-L3



to bridge VLAN1 to the other switch for management.



We do want to trunk two VLANs so they can be routed to our other subnets. To simmulate



the Nortel switch, I am using the Cisco 3548 to work out the configuration.



What I have done is created the VLANs on the Cisco 3548. Configured fa0/1 as a trunk.



I am using dot1q as the trunk protocol. Configured the trunk to allow only VLANs 1,


100, and 200. Vtp is set to transparent.

On the Cisco 2948G-L3 I configured fa44 with three subinterfaces:fa44.1, fa44.100, and



fa44.200. They are configure with dot1q and fa44.100 and fa44.200 have ip addresses



assigned. I made fa44.1 a member of bridge-group 111.



BVI111 on the Cisco 2948G-L3 has ip address 192.168.11.1 255.255.255.0 and VLAN 1 on the



Cisco 3548 has ip address 192.168.11.2 with a default gateway of



192.168.11.1.


-- A Basic Question:



I am assuming that the subinterfaces fa44.100 and fa44.20 on the Cisco



2948G-L3 will

route to the other BVIs. Is this correct?


-- My Problem So Far:



My bridging of VLAN1 does not work as I cannot ping the VLAN1 ip addresses across the



trunk. I have not tried the other subnets yet, but if the bridging doesn't work the



others probably aren't either.



Is there a way to confirm the trunk is working? The interfaces line protocols are up.


Here is the config of my subinterfaces on the Cisco 2948G-L3 where the trunk comes in.



interface FastEthernet44 no ip address no ip directed-broadcast ! interface FastEthernet44.1 encapsulation dot1Q 1 native no ip directed-broadcast bridge-group 111 ! interface FastEthernet44.100 encapsulation dot1Q 100 ip address 192.168.8.1 255.255.255.0 ip helper-address 192.168.3.4 no ip directed-broadcast ! interface FastEthernet44.200 encapsulation dot1Q 200 ip address 192.168.10.1 255.255.255.0 ip helper-address 192.168.3.4 no ip directed-broadcast


Here is the trunk on the Cisco 3548



interface FastEthernet0/1 switchport trunk encapsulation dot1q switchport trunk allowed vlan 1,100,200,1002-1005 switchport mode trunk



Any suggestions will be appreciated.



Finally got it working. I had forgotten the route ip command on the new BVI, bridgegroup 111.

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