Cisco 887 playing well with Cisco 3750

[Neil Haswell]

I have obtained the above equipment and I am trying to get it all working together nicely.

Essentially I want the Cisco 887 router (which only has L2 interfaces) to route all the vlans defined on the 3750 out through the DSL line Dialer0

When I connect various laptops in various vlans to the the 3750 i can ping each other.

So for example:

laptop on vlan 10 with ip 192.168.10.10 can ping laptop on vlan 20 with ip 192.168.20.10. Good news.

The 887 is on vlan 1 (i know it is bad to be vlan1 dont shout at me) with IP 192.168.0.254

If i have a laptop on 192.168.0.10 it can ping the 887 and the other vlans but I cannot get a laptop on 192.168.20.10 (vlan1) to ping 192.168.0.254 the router.

I can emulate this also by pinging 192.168.0.254 source vlan 10 from the 3750.

Now if I create vlans on the 887 like this.

int vlan 10

ip address 192.168.10.254

no shut

then it works.

But I was just expecting the 3750 to handle all the intervlan routing and to forward it onto the router to pass it out through to the internet.

Am I missing somthing fundamental in my knowledge / expectations.?

Many thanks

N

[Jon Marshall]

Neil

Can you post configs of 3750 and the 887 ?

Jon

[Neil Haswell]

I would but I know my config is wrong as it doesnt work.

Essentially I am asking more about the principal of intervlan routing from a 3750 to a 887.

At present I have pretty much flattened the environment to start again.

[Jon Marshall · Accepted solution]

I would but I know my config is wrong as it doesnt work.

Well that's why i asked for it to see what is wrong with it

For inter-vlan routing with a 3750 and 887 assuming you are doing the inter-vlan routing on the 3750 then you simply create all your vlans and the L3 vlan interfaces on the 3750. Then if you are using a L2 port on the 887 you simply have a common vlan between the 3750 and 887. You would then need a L3 vlan interface on the 3750 and an equivalent interface on the 887 eg. -

3750

====

int gi0/1  <--- connects to 887

switchport

switchport mode access

switchport access vlan 20

int vlan 20

ip address 192.168.10.1 255.255.255.252

887

===

L2 interface eg.

int fa0/1

switchport

switchport mode access

switchport access vlan 20

int vlan 20

ip address 192.168.10.2 255.255.255.252

Note i have use a dedicated vlan ie.vlan 20 for the 3750 to 887 connectivity and hence i only used a /30 subnet ie. 192.168.10.0/30.

then you need to take care of routing -

on the 3750 you simply need a default-route pointing to the 887 eg.

ip route 0.0.0.0 0.0.0.0 192.168.10.2

on the 887 you need routes for all subnets/vlans that are on the 3750 eg.

ip route 192.168.1.0 255.255.255.0 192.168.10.1

ip route 192.168.2.0 255.255.255.0 192.168.10.1

etc..

or you could just use a summary route eg.

ip route 192.168.0.0 255.255.0.0 192.168.10.1 <-- this assumes all 192.168.x.0 networks are on the 3750 ie. they are not reached via any other device.

You can if you want run a routing protocol between the 3750 and the 887 but it depends on the IOS feature set on your 3750.

Jon