Cisco Multilink PPP Configuration over Serial Links between Routers

Cisco Multilink PPP used to bundle two or more Serial links or BRI/PRI channels. When we upgraded an existing Serial/E1/T1 link with one more parallel Serial/E1/T1 link, it is easy to bundle Serial links by using Multilink PPP. If the first E1/ T1 circuit is a point to point circuit, first you must make sure that encapsulation is Point to Point protocol, as apposed to HDLC. This we can do by using the simple command encapsulation ppp on the serial interface of each router. Once this is done, a second circuit is easy to add by creating a Multilink interface.

The following configuration example will connect Router1 and Router2 by using a multilink interface to bundle the 2 serial links (serial1 1/5:0 and serial 4/0).

Cisco Multilink PPP Configuration Steps

Router 1 Configuration:

interface Multilink1
description ##Multilink PPP##
ip address xxx.xxx.xxx.xxx xxx.xxx.xxx.xxx
ppp multilink
ppp multilink fragment disable
ppp multilink links minimum 1
ppp multilink group 1

You can find layer 3 (IP Address) configuration now goes on the Multilink interface and along with the number/identifier of the multilink group. The ppp multilink links minimum command, the Network Control Protocols for an MLP bundle are disabled until the bundle has the minimum number of configured links. Packet fragmentation is enabled on the multilink interface by default, you can disable this fragmentation if it causes performance degradation.

Now configure PPP encapsulation and group membership on the serial interfaces that are participating in the Multilink PPP

interface Serial 1/5:0
description ##Multilink PPP – 1##
no ip address
encapsulation ppp
ppp multilink
ppp multilink group 1

interface Serial 4/0

description ##Multilink PPP – 2##
no ip address
encapsulation ppp
ppp multilink
ppp multilink group 1

Router 2 Configuration:

interface Multilink1
description ##Multilink PPP##
ip address xxx.xxx.xxx.xxx xxx.xxx.xxx.xxx
ppp multilink
ppp multilink fragment disable
ppp multilink links minimum 1
ppp multilink group 1

interface Serial 1
description ##Multilink PPP – 2##
no ip address
encapsulation ppp
ppp multilink
ppp multilink group 1

Filed Under: Serial

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  1. Ritesh says:

    Yes, Cisco Multi link PPP works great. I am currently bonding 5 T1’s and getting ready to add a 6th on a 2651XM. Ask if your ISP supports MLPPP.

  2. Sagar says:

    This blog has inspired me to start working on my own blog

  3. George says:

    I am continuously looking online for articles that can benefit me. Thanks for sharing Cisco MLPPP configuration.

  4. Justin says:

    Way cool, some valid points! I appreciate you making this article available about Multilink PPP configuration on Cisco Routers, the rest of the site is also high quality. Have a fun.

  5. Shul says:

    Interesting topic on MLPPP configuration on Cisco Router, thanks.

  6. James says:

    Your style is so unique compared to other folks I have read stuff from. I appreciate you for posting when you have the opportunity, Guess I’ll just book mark this blog.

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