How do you configure Multilink PPP on Cisco Routers
How do you configure Multilink PPP?
Given that the two sites that are connecting via Multilink PPP communicate with each other and coordinate the configuration, configuring Multilink PPP is easy. Here is a sample configuration of 3E1 circuits being bonded to form a single 6Mb Internet circuit:
controller E1 4/0
framing NO-CRC4
channel-group 1 timeslots 1-31
description Connect to OtherSite#1
!
controller E1 4/1
framing NO-CRC4
channel-group 1 timeslots 1-31
description Connect to OtherSite#2
!
controller E1 4/2
framing NO-CRC4
channel-group 1 timeslots 1-31
description Connect to OtherSite#3
!
interface Multilink1
ip address 1.1.1.1 255.255.255.252
no cdp enable
ppp multilink
ppp multilink group 1
!
interface Serial4/0:1
no ip address
encapsulation ppp
no fair-queue
ppp multilink
ppp multilink group 1
!
interface Serial4/1:1
no ip address
encapsulation ppp
no fair-queue
ppp multilink
ppp multilink group 1
!
interface Serial4/2:1
no ip address
encapsulation ppp
no fair-queue
ppp multilink
ppp multilink group 1
!
This configuration is from a Cisco 7200 router that has Qty 1 Controllers E1 interfaces (plugged into module 4). These E1 controllers create the Serial4/0:1, Serial4/1:1, Serial4/2:1 interfaces that are bound to the multilink group #1, and other serial interfaces (Serial4/3:1, Serial4/4:1 and so on...)
It is the multilink1 interface that is actually the single combined interface that really has the “6Mb” of bandwidth, and that is where you would apply all of your “normal interface configuration” for this 6Mb connection that connects to the Internet. You can see how the multilink 1 interface has an interface number that matches the ppp multilink group. On that multilink 1 interface, you have the IP address for this link, an ACL on the interface, firewall, NAT, or other router interface commands.
By using the multilink interface, you are able to bond all three of these E1 interfaces into a single router interface — very cool!
To verify that your multilink interfaces are up and running, you can use the show ppp multilink command, like this:
Router# show ppp multilink
Multilink1, bundle name is OtherSite
Bundle up for 3w4d, 89/255 load
Receive buffer limit 85344 bytes, frag timeout 1000 ms
10518/6985 fragments/bytes in reassembly list
21651 lost fragments, 3287247349 reordered
17098/8879018 discarded fragments/bytes, 18 lost received
0xA990C7 received sequence, 0x7F6AA8 sent sequence
Member links: 3 active, 0 inactive (max not set, min not set)
Se4/0:1, since 3w4d
Se4/1:1, since 3w4d
Se4/2:1, since 3w4d
Router#
The key to configuring Multilink PPP is the multilink interface, the ppp multilink protocol on each router, and the ppp multilink group x command on each interface. Multilink PPP isn’t a difficult router configuration to set up, and it is extremely valuable when you need multiple circuits bonded into a single circuit from a single provider.
And for sure, you can just add multilink interface to be routed using OSPF, PBR or any other routing protocol.
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