From: Edwards, Andrew M (andrew.m.edwards@boeing.com)
Date: Fri Apr 08 2005 - 13:52:34 GMT-3
Mani,
VRRP / HSRP will provide a virtual IP address that provides fault
tolerance for default gateway failover with network clients that DO NOT
understand multiple gateways. IOW, you specify one default gateway that
is the virtual address on the client. The client is not smart enough to
distinguish multiple gateways and priorities, so you implement a network
infrastructure based solution to this problem.
Neither VRRP or HSRP advertise their gateways to clients.
This is a function of other protocols such as DHCP or IRDP.
DHCP provides a gateway of last resort. DHCP can provide multiple
gateways as well.
IRDP is ICMP Router Discovery Protocol. IRDP aware hosts will pickup
the subnet broadcast (or multicast if configured) specifying one or more
default gateways to use with specific preferences. I believe the
highest preference wins (unless you are a cisco router acting as the
host in which case its lower wins).
So, what I'm driving at is a multi-part solution.
How to advertise the gateway? DHCP / IRDP
How to ensure that one router is master of the gateway IP and another
takes over if the master is unavailable? HSRP / VRRP
If you go for the when in doubt method, I suggest as always, ask the
proctor for clarification. If however you find you dont have time to
ask, or you are unsatisfied with the proctors response, you could do
IRDP as well as DHCP.
This is just CYA.
Just dont break anything else if you do both.
HTH
Andy
-----Original Message-----
From: mani poopal [mailto:mani_ccie@yahoo.com]
Sent: Thursday, April 07, 2005 4:02 PM
To: Edwards, Andrew M; marvin greenlee; ccielab@groupstudy.com
Subject: RE: vrrp vs irdp [bcc][faked-from][bayes]
Marvin/Edword,
Thanks for the links. When configuring dhcp and vrrp . How
many default router we specify with dhcp. Edword you said when in dobt
configure both vrrp and irdp. I thought with dhcp and irdp, you don't
advertise a default router and client must be aware for irdp. If the
question specifies to advertise a default router, I think we cannot use
irdp. Please clarify on this.
For dhcp/vrrp-->which of the following combination is correct.
===================================================
default-router 10.10.10.100<--VIRTUAL IP ADDRESS(USED IN HSRP)
or
default-router 10.10.10.3 10.10.10.5(R3,Primary ethernet and R5
ethernet ip address)
===================================================
PS:Can we configure both vrrp and irdp, When with dhcp/irdp do
we define a default-router(gateway) for the clients
thanks
Mani
"Edwards, Andrew M" <andrew.m.edwards@boeing.com> wrote:
When in doubt, configure both IRDP and VRRP.
Set IRDP such that R1 and R3 are proxy for the GW IP
address issued by
DHCP, which also would need to be the VRRP virtual IP.
8)
I love this lab!
-----Original Message-----
From: marvin greenlee [mailto:marvin@ccbootcamp.com]
Sent: Thursday, April 07, 2005 1:34 PM
To: 'mani poopal'; ccielab@groupstudy.com
Subject: RE: vrrp vs irdp [bcc][faked-from][bayes]
VRRP is very similar to HSRP, in that you have an
elected virtual router
that forwards packets sent to a virtual IP address.
With DHCP, you have the option of specifying multiple
gateways, but it
is up to the end hosts to determine whether a gateway
has failed, and to
switch to using the next gateway.
IRDP announces a gateway. By itself, it is not
recommended for failure
detection, due to the spac! in! g between
advertisements. IRDP can be used
in conjunction with VRRP, and can advertise the IP
address of the
virtual address, by setting a priority value.
GLBP is similar to VRRP and HSRP, but multiple routers
are active and
the packet forwarding is balanced.
IRDP - RFC 1256
http://www.faqs.org/rfcs/rfc1256.html
VRRP - RFC 3768
http://www.faqs.org/rfcs/rfc3768.html
Cisco - GLBP - Gateway Load Balancing Protocol -
http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_
guid
e09186a00801541c8.html
Marvin Greenlee, CCIE#12237, CCSI# 30483
Network Learning Inc
marvin@ccbootcamp.com
www.ccbootcamp.com (Cisco Training)
-----Original Message-----
From: nobody@groupstudy.com
[mailto:nobody@groupstudy.com] On Behalf Of
mani poopal
Sent: Thursday, April 07, 2005 1:08 PM
To: ccielab@groupstudy.com
Subject: vrrp vs irdp [bcc][faked-from][bayes]
Importance: LowHi Guys,
I have a question regarding gateway redundency. If R1 &
R3 are
connected by ethernet link(vlan 10) and R3 is the dhcp
server. We have
to make R1 as a primary link and R1 as gateway when only
primary
fails(Restriction:Not to use hsrp feature)
R1-----VLAN 10 USERS--------R3(DHCP SERVER)
If a question does not ask to track and interfaces and
not telling any
thing about irdp asware status of clients. What feature
can be
used(vrrp or irdp). Any help is appreciated with good
example.
PS:what is the difference between vrrp and irdp and
under what
circumstenses we use these features.
thanks
Mani
B.ENG,A+,CCNA,CCNP,CCNP-VOICE, CSS1,CNA,MCSE
(416)431 9929
MANI_CCIE@YAHOO.COM
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