Any way to Bundle/Group T1 and ehternet port on cisco3845 router?

[saif akbar]

I have cisco 3845 router. Currently we are using T1 line between two locations but recently we upgraded to TW Telecom Eline 4Meg. TW telecom handoff me an ehternet connection, they bundeled 3 T1  together.

Now i want to use the existing t1 as it is but i also want to use ethenet handoff (provided by tw telecom). This setup is same on the other side.

Is there any way i can bundle or group T1 and ethernet ?

i tried multilink on serial, but under ethernet port i donn't see multilink command.

[Dennis Mink · Accepted solution]

Are you saying you want to bundle the ethernet drop (which is limited to 4Mbps) with an additional T1 (1.544Mbps)  making it a link of 5.5Mbps?

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[saif akbar]

Yes. I am using cisco 3845 series router.

[Richard Burts]

Multilink is intended for PPP encapsulated serial links. So you can multilink multiple T1 interfaces. But there is not any support for multilink with Ethernet. If you want to make use of both links I would suggest that you set up routing on both routers to use the Ethernet as the preferred link (and T1 as a backup) and then configure Policy Based Routing to select certain traffic (perhaps something like Email or file transfers, or something) and send that traffic over the T1. This would allow you to effectively use both of the links. I have implemented this type of strategy and it works well.

HTH

Rick

[saif akbar]

can i get some configuration example ?

[Richard Burts]

For this example let us assume that the interfaces and addresses of one router are

FastEthenet0/0 172.16.1.1 255.255.255.0 Ethernet from telecom connecting to remote router.

FastEthernet0/1 172.16.2.1 255.255.255.0 subnet where users are connected.

Serial1/0 172.16.3.1 255.255.255.0 serial connecting to remote router.

for policy based routing you would follow steps similar to these

first configure an access list to identify the traffic that will be policy routed.

access-list 151 permit tcp 172.16.2.0 0.0.0.255 any eq www (choosing web traffic)

then configure a route map to use the access list and to set the next hop

route-map PBR permit 10

match ip address 151

set ip next-hop 172.16.3.2

then configure the interface where the traffic arrives to use PBR

interface Fastethernet0/1

ip policy route-map PBR

For further information about policy based routing you might start with this link

http://www.cisco.com/en/US/docs/ios/12_2/qos/configuration/guide/qcfpbr_ps1835_TSD_Products_Configuration_Guide_Chapter.html

HTH

Rick

[saif akbar]

that's very helpful.

Still a confusion though, let's say i only want to use one subnet between two locations 172.16.1.1 my end and 172.16.1.1 on other end. I can route all traffic going to remote location by implementing a static route, see below;

ip route 10.0.35.0(network on remote end) 255.255.255.0 172.16.1.2

Can i just do something so all interfaces can act as a group or bundeling and whenever traffic going to 10.0.35.0 network can simpley take 172.16.1.2 route ?

Also, is it possible to bundle two carriers/ISPs ?

[Richard Burts]

I am not understanding your question. In general if you have two links and you want each link to carry IP traffic then each link needs to have an IP subnet and each interface needs to have an IP address. I can think of only one way to have 2 links and have only 1 subnet. You could configure the IP address on the ethernet interface and on the serial interface you could do ip unnumbered using the address from the ethernet.

While I can say that you can do this and the router will accept the commands, I am not sure how that would work and believe that you would not be happy about the result. Assuming that you did the interface configuration this way and configured the static route then the router will have two links that appear to get to the next hop. So the router will send one packet over the ethernet, send the next packet over the T1, then next over ethernet, then next over T1, and so forth. The result is either that the T1 is extremely overloaded and may drop many packets or the result is that the ethernet is underloaded. I think that neither of these is desirable.

If you have a 4 Meg connection and a 1.5 Meg connection the most effective way to use both is the PBR that I suggested.

HTH

Rick