Simple Multilink PPP setup

Here is a receipt to create a multilink with serial (T1/E1) interfaces. I think the configuration snippet could be adapted to T3/E3 interfaces too, but i didn’t test it…

I kept the setup very simple, but perhaps i will add some notes about features or troubleshooting later.

multilink

Serial interface configuration

interface Serial1/0:0
 description Link to jenny s1/0
 no ip address
 encapsulation ppp
 ppp multilink
 ppp multilink group 47
!
interface Serial1/1:0
 description Link to jenny s1/1
 no ip address
 encapsulation ppp
 ppp multilink
 ppp multilink group 47
!
interface Serial1/2:0
 description Link to jenny s1/2
 no ip address
 encapsulation ppp
 ppp multilink
 ppp multilink group 47
!
interface Serial1/3:0
 description Link to jenny s1/3
 no ip address
 encapsulation ppp
 ppp multilink
 ppp multilink group 47
!

Configuration for jenny can be done by the same way.

Creating virtual interface “Multilink47″

maria:
interface Multilink47
 description Multilink to jenny mu47
 ip address 10.99.99.1 255.255.255.252
 ppp multilink
 ppp multilink group 47
jenny:
interface Multilink47
 description Multilink to maria mu47
 ip address 10.99.99.2 255.255.255.252
 ppp multilink
 ppp multilink group 47

Test, if it works

You can verify the configuration by pinging 10.99.99.2 from maria:

maria#ping 10.99.99.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.99.99.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/26/52 ms
maria#

For gathering further informations about the multilink, you could use the “sh ppp multilink” command:

maria#sh ppp multilink
Multilink47
  Bundle name: jenny
  Remote Endpoint Discriminator: [1] jenny
  Local Endpoint Discriminator: [1] maria
  Bundle up for 00:09:22, total bandwidth 6176, load 1/255
  Receive buffer limit 48000 bytes, frag timeout 1000 ms
    0/0 fragments/bytes in reassembly list
    0 lost fragments, 266 reordered
    0/0 discarded fragments/bytes, 0 lost received
    0x172 received sequence, 0x172 sent sequence
  Member links: 4 active, 0 inactive (max not set, min not set)
    Se1/3:0, since 00:09:20
    Se1/0:0, since 00:09:21
    Se1/1:0, since 00:09:21
    Se1/2:0, since 00:09:21
No inactive multilink interfaces
maria#

In the output, you can see the following:

  • what’s the endpoints PPP hostname (brown)
  • when was the multilink established (green)
  • when did the participating interfaces joined the multilink (blue)
  • (other counters will be explained later)

Example output with 2 faulty serial links (red):

maria#sh ppp multilink
Multilink47
  Bundle name: jenny
  Remote Endpoint Discriminator: [1] jenny
  Local Endpoint Discriminator: [1] maria
  Bundle up for 01:52:48, total bandwidth 3088, load 1/255
  Receive buffer limit 24000 bytes, frag timeout 1000 ms
    0/0 fragments/bytes in reassembly list
    0 lost fragments, 288 reordered
    0/0 discarded fragments/bytes, 0 lost received
    0x1CC received sequence, 0x1CE sent sequence
  Member links: 2 active, 2 inactive (max not set, min not set)
    Se1/3:0, since 01:52:47
    Se1/0:0, since 01:52:47
    Se1/1:0 (inactive)
    Se1/2:0 (inactive)
No inactive multilink interfaces
maria#

The multilink interface is working through the last interface leaves the bundle.

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