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Routable Ethernet ports in 2811 ISRs

Hello,

Here is my set up

ISP A - Serial T1 CSU/DSU

ISP B - Fa 0/0Ehternet T1 (used for a different LAN)

Internal Network - Fa 0/1

2811 router - 1 CUS/DSU WIC & 2 Fast Ethernet ports

I am planning to increase my T1 capacity and ISP A says they will provide an managed T1 link with ethernet handoff, so my existing WIC becomes unusable.

My 2811 has only two routable fast ethernet ports.

If I plan to terminate my new Ethernet handoff in Fa0/1 (Where my existing LAN link is connected) and use an ether switch module to connect the LAN

Will this be an ideal solution. What factors should I take into consideration for implementing this solution

Thanks,

Chandru

1 ACCEPTED SOLUTION

Accepted Solutions
Blue

Re: Routable Ethernet ports in 2811 ISRs

Tim is correct. You just create a VLAN interface for the VLAN you assign to the switchport. The only limitation I am aware of is you can't run BGP (at least that's the way I read the docs) with the EtherSwitch, but EIGRP or OSPF works fine.

I have this exact setup on two 2821s, so I can assure you it works.

4 REPLIES
Blue

Re: Routable Ethernet ports in 2811 ISRs

Your solution keeps it simple, but does require spending money.

An alternative would be to connect the ISPs to your LAN switch on unique VLANs and configure a 802.1Q trunk to the router with a subinterface per ISP/VLAN.

If it was me I would go with the Etherswitch WIC. It will simplify any needed traffic shaping and QOS config.

Please rate helpful posts.

New Member

Re: Routable Ethernet ports in 2811 ISRs

Hi dgahm,

I went through the FAQs for Etherswitch WIC, I found the following

Q. Can the individual ports be configured as routed ports?

A. No, the Cisco EtherSwitch HWICs do not support routed ports. This means you cannot assign an IP address directly to the interface and make it a Layer 3 interface.

If I am not able to assign an IP address how would I be able to configure the router internal interface

Thanks,

Chandru

Gold

Re: Routable Ethernet ports in 2811 ISRs

These work like a layer3 switch. You define vlan interfaces and assign the ports to a vlan.

You can put each port in its own vlan if you wish and you in effect have a routed interface

Blue

Re: Routable Ethernet ports in 2811 ISRs

Tim is correct. You just create a VLAN interface for the VLAN you assign to the switchport. The only limitation I am aware of is you can't run BGP (at least that's the way I read the docs) with the EtherSwitch, but EIGRP or OSPF works fine.

I have this exact setup on two 2821s, so I can assure you it works.

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