Correct MLPPP configuration for T1s

Unanswered Question
Jun 11th, 2009

I'm trying to develop a good template for bonding T1s together using MLPPP.

So the member serial interfaces need to have WFQ disabled or keep it enabled? Should CEF be disabled on the multilink interface or should it be left enabled? I'm trying to figure out how multilink load balances traffic across the member links and if any of the queueing or route switching upsets that.

It should be noted that we are using CBWFQ on the multilink interface with class-maps that use NBAR. Below is a sample of what we're working with today:

interface Multilink26

description Multilink interface

ip unnumbered Loopback0

ip verify unicast reverse-path

no ip redirects

ip nbar protocol-discovery

no ip route-cache cef

ppp multilink

ppp multilink group 26

no cdp enable

service-policy output VoIP-qos

!

interface Serial1/0/24:0

description Member link

bandwidth 1544

ip unnumbered Loopback0

ip verify unicast reverse-path

no ip redirects

no ip proxy-arp

encapsulation ppp

no fair-queue

ppp multilink

ppp multilink group 26

!

interface Serial1/0/25:0

description Member link

bandwidth 1544

ip unnumbered Loopback0

ip verify unicast reverse-path

no ip redirects

no ip proxy-arp

encapsulation ppp

no fair-queue

ppp multilink

ppp multilink group 26

Any ideas on what we should be doing differently. This is from a 7206VXR with PA-MC-2T3-EC cards and the other side is a non-cisco device.

I have this problem too.
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mlitka Thu, 06/11/2009 - 09:45

Here is an example of a config we use on a 2811. This seems to work well:

interface Multilink1

bandwidth 3000

ip address x.x.x.x 255.255.255.252

ip mtu 1496

ip tcp adjust-mss 1400

no peer neighbor-route

no cdp enable

ppp chap hostname xxx

ppp multilink

ppp multilink fragment disable

ppp multilink links minimum 1

ppp multilink group 1

service-policy output qos_queue

interface Serial0/2/0:0

bandwidth 1536

no ip address

encapsulation ppp

no keepalive

no fair-queue

ppp chap hostname xxx

ppp multilink

ppp multilink group 1

!

interface Serial0/2/1:0

bandwidth 1536

no ip address

encapsulation ppp

no keepalive

no fair-queue

ppp chap hostname xxx

ppp multilink

ppp multilink group 1

tmarlow Thu, 06/11/2009 - 11:09

What's the reason for "no fair-queue" on the serial interface.

mlitka Thu, 06/11/2009 - 11:25

I believe IOS puts it on by default on higher bandwidth links. I don't believe it is necessary.

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