From: Sean Connelly (Sean_E_Connelly@hotmail.com)
Date: Tue Nov 02 2004 - 11:06:27 GMT-3
Hello,
I believe Bob is right, and what is in the CD is misleading (imagine that)
but not necessarily wrong. I think the whole issue comes down to what one
defines as a 'host'. When a router is acting as the IRDP gateway for a
"PC-host" - the PC-host will use the IRDP-enabled router with the higher
value. When a router is acting as the IRDP gateway for a "ROUTER-host", the
ROUTER-host uses the IRDP-enabled router with the lower value. Since IRDP
is used more to support PC-hosts rather than support ROUTER-hosts, most docs
just discuss how to support a PC-host, not how to configure IRDP-enabled
routers to support a ROUTER-host.
What the person listed as 'Cisco Net' does provide from the CCO:
(Optional) Preference value. The allowed range is -231 to 231. The default
is 0. A higher value increases the preference level of the router. You can
modify a particular router so that it will be the preferred router to which
other routers will home.
Should really be taken as "A higher value increases the preference level of
the router IF THE END HOST IS A PC."
And the next line "You can modify a particular router so that it will be the
preferred router to which other routers will home." - doesn't necessarily
state which value a ROUTER will use when talking to a IRDP-enabled router.
Yes, the sentence before states a higher value - but the 2 sentences
shouldn't necessarily be read together when using a ROUTER as a host.
So, the config depends on what is used as the host. If a router is used as
a host, you'll need to configure the more preferred IRDP router with a lower
value. If a PC is used as a host, you'll need to configure the more
preferred IRDP router with a higher value. As Gladstone had pointed out,
there was a great thread on this NMC's studyboard - I believe the values
even get more confusing than stated here (but no need to cloud the issue).
Also, just to prove a point:
In my lab, I've configured R5, R6 and FRS on the same LAN 56.56.56.0/24.
I've enabled R5 & R6 as IRDP routers, and have made FRS a ROUTER-host. You
configure a router as a host and have it look for use IRDP-enabled routers
as gateways by configuring 2 commands: 'no ip routing' and 'ip gdp irdp'.
As can be seen on FRS (the ROUTER-host), R5 with a IRDP preference of 5, is
used by FRS as it's preferred gateway rather than R6 - which has a IRDP
value of 6.
FRS#show ip route
Gateway Using Interval Priority Interface
56.56.56.5 IRDP 900 5 Ethernet0
56.56.56.6 IRDP 900 6 Ethernet0
Default gateway is 56.56.56.5
R5 config:
interface Ethernet0/0
ip address 56.56.56.5 255.255.255.0
ip irdp
ip irdp preference 5
R6 config:
interface Ethernet0
ip address 56.56.56.6 255.255.255.0
ip irdp
ip irdp preference 6
FRS config:
no ip routing
ip gdp irdp
interface Ethernet0
ip address 56.56.56.7 255.255.255.0
HTH,
Sean
----- Original Message -----
From: "Cisco Net" <network.cisco@gmail.com>
To: "Bob Sinclair" <bsin@cox.net>
Cc: "Joe Rothstein" <ziutek@mac.com>; "Group study" <ccielab@groupstudy.com>
Sent: Sunday, October 31, 2004 1:26 PM
Subject: Re: irdp preference
> Confused with all these informations..
>
:)http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fi
pras_r/1rfipadr.htm#wp1018753
> Says high value prefer right ???
> Cert
>
>
> On Sun, 31 Oct 2004 10:13:33 -0500, Bob Sinclair <bsin@cox.net> wrote:
> > Joe,
> >
> > Whether higher or lower preference is preferred depends on the host.
> > Normally, the router is acting as a gateway and the preference is sent
to PC
> > hosts. PC hosts prefer the gateway with the higher preference. This
is
> > what is reflected in the router syntax:
> >
> > R2(config-if)#ip irdp preference ?
> > <-2147483648 - 2147483647> preference for this address (higher values
> > preferred)
> >
> > BUT, we often turn our cisco routers into hosts in lab scenarios by
turning
> > off IP routing. The cisco router, as a host, will choose the gateway
with
> > the lowest configured preference number. When checking this on
equipment,
> > be sure to be patient. The irdp hello and hold times are quite long.
> >
> > HTH,
> >
> > Bob Sinclair
> > CCIE #10427, CISSP, MCSE
> > www.netmasterclass.net
> >
> >
> >
> > ----- Original Message -----
> > From: "Joe Rothstein" <ziutek@mac.com>
> > To: "Group study" <ccielab@groupstudy.com>
> > Sent: Saturday, October 30, 2004 8:01 AM
> > Subject: irdp preference
> >
> > > Could someone give me a definitive answer as to the preference under
IRDP?
> > >
> > > Looking at the documentation it is unclear as to whether a higher
> > > preference or lower preference makes a router the preferred gateway.
> > >
> > > Any comments and clarification would be appreciated.
> > >
> > > Joe
> > >
> > >
This archive was generated by hypermail 2.1.4 : Thu Dec 02 2004 - 06:57:37 GMT-3