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From: Hank Nussbacher <HANK@VM.BIU.AC.IL>
Newsgroups: comp.dcom.sys.cisco
Subject:      Re: Load Balancing
Message-ID: <35406@boulder.Colorado.EDU>
Date: 28 May 91 08:50:52 GMT
Sender: daemon@boulder.Colorado.EDU
Lines: 33

>Subject: Load Balancing between Equal Cost Routes
>
>If two serial links terminate at a the same cisco router at one end and to
>the same node at the other end, will a cisco router recognise that there
>are multiple equal cost routes to that node, and places beyond?
>Can it be made to distribute transmitted packets between the two links?
>What algorithm does it use?
>Is any inter-router protocol required to be supported by the other node?
>
>Protocols of interest are PPP, TCP/IP, etc.

It all depends what you are routing and also whether you are bridging.
If you are routing TCPIP traffic it depends on what routing protocol
is being used.  RIP will not load balance, but IGRP will do a reasonable
job of balancing the load on the two lines.  If you are routing
DECNET via Phase IV you will not be using one line at all and it will
be more or less a hot standby.  If the cost is the same on both lines
the DECNET routing protocol will still only use one line.  Phase V will
load balance between the two lines.

If you are bridging, then the cisco splits the load based on Ethernet
addresses.  It assigns some Ethernet addresses to one line and some
to another line.  This does a reasonable job of utilizing both lines.
But if you have only one Ethernet station at the end of your two lines
then the cisco will only utilize one of the two lines since it can't
split the load among more Ethernet addresses.

>
>Thanks,
>-Tim.

Hank Nussbacher
Israel