From: Brian Hescock (bhescock@xxxxxxxxx)
Date: Tue Nov 20 2001 - 10:36:47 GMT-3
Parry,
Ping doesn't do per packet load balancing per se, it's a matter of
where you do the ping and how the router that is being traversed is
configured. Example:
R1--R2---R3--10.1.1.1
Ping from R1 to 10.1.1.1. The ping packet is process-switched on R1 since
the packet is originated on the router. But on R2 the packet could be
either process-switch, fast-switched, cef switched, parallel-express
forwarding, etc, depending upon the platform and type of switching
configured on the router / interface. In terms of load balancing, it
reacts different with each switching path and is something that should be
studied for you day-to-day operations, not just for the lab.
Brian
"Chua, Parry" wrote:
> Hi,
>
> There is two way of load share ? balanceing ? in Cisco router
> implementation, per packet and per destination. With route cache turn
> on, per destination load share/balance is used. I know ping will do per
> packet load balancing, ie one packet go interface1 and next interface2
> and son on.
>
> Parry Chua
>
> -----Original Message-----
> From: Hansang Bae [mailto:hbae@nyc.rr.com]
> Sent: Tuesday, November 20, 2001 12:03 PM
> To: ccielab@groupstudy.com
> Subject: RE: OSPF Load Balance
>
> >>From: "Chua, Parry" <Parry.Chua@compaq.com>
> >>I thought that when we show IP route, there could be one or more path
> to
> >>reach a particular destination based on the routing protocol type. For
> >>OSPF, if we know there could be more than one path to reach that
> >>destination,
>
> Correct.
>
> >>we can then manuiplate the COST to get a equal cost
> >>for load balanceing, right ?
>
> Perhaps. Load Balancing is not as easy as people think.
>
> >>Other protocolos such as (E)IGRP support
> >>unequal cost load balancing. As for RIP, I belive we can use offset to
> >>change the hop count from unequal to
> >>equal and vice versa, right ?
>
> But keep in mind that fast processing's job is to limit the lookup of
> the
> routing table (forwarding table I guess). So even if you have two equal
>
> cost routes to a destination, by default, it will use one and only one
> link. If it didn't, it kinda defeats the purpose of fast-processing.
> If
> you do a "sho ip cache" you'll see what I mean.
>
> hsb
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