[nsp] HSRP

[k. scott bethke]

Great thread guys..  Also note that multigroup HSRP is a way to load balance
traffic, I always hated the fact that one router (or even just one router
interface) was standby why not use it?  With mutigroup you can setup two
VIP's essentually one homed on each interface and you can either point half
your servers to one or half your servers to the other and balance traffic
that way, or you can actually put two default routes on each server and it
will do the right thing and balance traffic out to both routers.

Has anyone noticed really strange issues with HSRP on dot1q based Vlan
interfaces using extreme networks gear as the switches?  I used to run a
network with really old 7500's and 7200's and we just had issues all the
time with the vlans not communicating randomly.  It would work fine and just
stop and then oneday just start working again.  Very strange.  A major issue
with HSRP in this capacity is that both interfaces claim the other has died
and BOTH take ownership of the VIP.  I can imagine that in this case a
unicast solution MAY work better than multicast.

-Scotty
----- Original Message ----- 
From: "Thomas Renzy" <thomas.renzy at veritas.com>
To: "'Peter B. Juul'" <peter.juul at uni-c.dk>; "mac" <mac at telvia.it>
Cc: <cisco-nsp at puck.nether.net>
Sent: Thursday, June 19, 2003 4:05 PM
Subject: RE: [nsp] HSRP


> Peter,
>
> HSRP uses Multicast and the address is 224.0.0.2. HSRP also uses UDP on
port
> 1985.
>
> You can also HSRP to track interfaces and to change the priority in case
> there is a problem with it. Here is an example of this.
>
> interface Vlan10
>  description Server-Vlan
>  ip address 10.1.1.2 255.255.255.0
>  standby ip 10.1.1.1
>  standby priority 120 preempt
>  standby track GigabitEthernet2/16 75
>
> Here this vlan is tracking interface G2/16. The number "75" tells how much
> the decrement the priority when the tracked interface goes down.
>
> Thomas
>
> Thomas Renzy
> IS&T Global Network Services
> VERITAS Software
> Office: +650-527-4734
> Mobile: +650-248-1099
> Fax: +650-527-2034
>
> "Some people drink from the fountain of knowledge, others just gargle." -
> Author Robert Anthony
>
>
>
> -----Original Message-----
> From: Peter B. Juul [mailto:peter.juul at uni-c.dk]
> Sent: Thursday, June 19, 2003 12:17 PM
> To: mac
> Cc: cisco-nsp at puck.nether.net
> Subject: Re: [nsp] HSRP
>
>
> On Thu, Jun 19, 2003 at 08:29:37PM +0200, mac wrote:
>
> > can one give me a quick explanation of HSRP is and how works?
>
> Sure. HSRP, Hot Standby Router Protocol.
>
> The concept is that you have two routers connected to the same Layer 2
> network, say 10.1.0.2/24 and 10.1.0.3/24.
>
> You configure the hosts on the net to use 10.1.0.1 as their default
> gateway and you then configure HSRP with a virtual IP address of 10.1.0.1.
>
> The routers then decide amongst each other which of them is to be 10.1.0.1
> now and the hosts use that router.
>
> Should that router die a horrible death (or should you decide to shutdown
> the interface, yank the wire or somesuch) the other router notices and
> quickly takes over the IP address and (as far as I remember) the MAC
address
> so the ARP tables doesn't make a fuss.
>
> You can set up priorities for the routers and you can ask them to
pre-empt,
> so that when the first router is back on line, it takes over again.
>
> It works a charm to my experience.
>
> (It is, afaik, the Cisco version of that which became VRRP. However, VRRP
> uses unicast for checking the status whereas HSRP uses multicast. Please,
> someone correct me if that's pure nonsense.)
>
> Peter B. Juul,
> Uni·C (PBJ255-RIPE)
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