From: Venkataramanaiah.R (vramanaiah@gmail.com)
Date: Tue Oct 31 2006 - 13:07:54 ART
thanks for jumping in.. Your understanding is correct.
However, we are building a loop free topology, where downlink for
Subnet A must always choose R1 and for Subnet B must always choose the
R2 path.. I cannot have the same subnet on both routers for this
reason..!
On 10/31/06, Vincent Mashburn <vmashburn@fedex.com> wrote:
> If I understand your predicament correctly here, you have 2 routers on
> the same physical segment, but each router is the gateway to a different
> subnet. If this is the case, why not make each router part of both
> subnets (via secondary addressing) and then use something like HSRP or
> VRRP (using 2 groups) to make Router 1 the primary for subnet 1 and
> Router 2 the primary for subnet 2? Just a thought... may be work
> trying.
> Thanks
> Vince Mashburn
> Voice / Data Engineer
> 901-263-5072
> CCVP, CCNP, CCDA,Network +
> Cisco IP Telephony Support Specialist
> Cisco IP Telephony Operations Specialist
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Venkataramanaiah.R
> Sent: Tuesday, October 31, 2006 3:01 AM
> To: Brian McGahan
> Cc: fangbo; Fosket, William; ccielab@groupstudy.com
> Subject: Re: Proxy-Arp with two routers on a segment..
>
> Brian is correct.. We tested this with Windows host and it behaves this
> way...
>
> However my legacy host some trouble while generating the arp requests,
> it always uses the first subnet IP while raising the arp request,
> although it owns both subnets on the same NIC. So at all times, Router
> of Subnet A is chosen.
>
> Regards
> -Venkat
>
> On 10/31/06, Brian McGahan <bmcgahan@internetworkexpert.com> wrote:
> > Tim,
> >
> > Assuming that proxy-ARP is enabled and that the host who
> > originates the ARP request has an IP address in the same subnet of the
> > interface that the router receives the ARP request on, then yes.
> >
> > Brian McGahan, CCIE #8593 (R&S/SP)
> > bmcgahan@internetworkexpert.com
> >
> > Internetwork Expert, Inc.
> > http://www.InternetworkExpert.com
> > Toll Free: 877-224-8987 x 705
> > Outside US: 775-826-4344 x 705
> > 24/7 Support: http://forum.internetworkexpert.com
> > Live Chat: http://www.internetworkexpert.com/chat/
> >
> >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> > Of
> > > fangbo
> > > Sent: Monday, October 30, 2006 10:33 PM
> > > To: Brian McGahan; 'Fosket, William'; 'Venkataramanaiah.R'
> > > Cc: ccielab@groupstudy.com
> > > Subject: re: Proxy-Arp with two routers on a segment..
> > >
> > > Hi there,
> > >
> > > I guess the host will send arp request to broadcast( FFFFFFFFFFFF),
> so
> > > every
> > > routers on same segment will get the request and send arp reply out
> if
> > he
> > > know the route to destination.
> > > Is this right?
> > > Thanks and regards,
> > >
> > > tim
> > > -----SJ<~T-<~-----
> > > 7"<~HK: nobody@groupstudy.com [mailto:nobody@groupstudy.com] 4z1m
> > Brian
> > > McGahan
> > > 7"KMJ1<d: 2006Dj10TB31HU 5:49
> > > JU<~HK: Fosket, William; Venkataramanaiah.R
> > > 3-KM: ccielab@groupstudy.com
> > > VwLb: RE: Proxy-Arp with two routers on a segment..
> > >
> > > > If an arp request from 1.1.1.2/24 were seen by a router at
> > 1.1.1.1/24
> > > > and a router at 2.2.2.1/24 on the same segment, would their be any
> > > > special configuration required to prevent 2.2.2.1 from answering?
> > >
> > > No extra configuration is needed. The router at 2.2.2.1/24
> will
> > > not respond to an ARP from 1.1.1.2 unless Local Area Mobility is
> > > enabled.
> > >
> > > Brian McGahan, CCIE #8593 (R&S/SP)
> > > bmcgahan@internetworkexpert.com
> > >
> > > Internetwork Expert, Inc.
> > > http://www.InternetworkExpert.com
> > > Toll Free: 877-224-8987 x 705
> > > Outside US: 775-826-4344 x 705
> > > 24/7 Support: http://forum.internetworkexpert.com
> > > Live Chat: http://www.internetworkexpert.com/chat/
> > >
> > >
> > > > -----Original Message-----
> > > > From: Fosket, William [mailto:William.Fosket@compass.net]
> > > > Sent: Monday, October 30, 2006 3:06 PM
> > > > To: Brian McGahan; Venkataramanaiah.R
> > > > Cc: ccielab@groupstudy.com
> > > > Subject: RE: Proxy-Arp with two routers on a segment..
> > > >
> > > > It's more of an issue of where the request is coming from than
> where
> > > > they are trying to get to, I think. It is more a question about
> how
> > > arp
> > > > works than how proxy arp works. Though the requests would come
> from
> > > the
> > > > same segment, they'd be coming from different subnets (if I
> > understood
> > > > correctly).
> > > >
> > > > If an arp request from 1.1.1.2/24 were seen by a router at
> > 1.1.1.1/24
> > > > and a router at 2.2.2.1/24 on the same segment, would their be any
> > > > special configuration required to prevent 2.2.2.1 from answering?
> > > >
> > > > Bill Fosket CCIE #16041
> > > >
> > > > -----Original Message-----
> > > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> Behalf
> > > Of
> > > > Brian McGahan
> > > > Sent: Monday, October 30, 2006 1:47 PM
> > > > To: Venkataramanaiah.R
> > > > Cc: ccielab@groupstudy.com
> > > > Subject: RE: Proxy-Arp with two routers on a segment..
> > > >
> > > > The ARP request will always come in from a host on a directly
> > > > connected segment. If the router has a route to the ARP's
> > destination
> > > > and proxy-arp is enabled on the connected link that the ARP was
> > > received
> > > > the router will reply with its own MAC address. The destination
> > does
> > > > not have to be connected, it just has to be in the routing table.
> > > >
> > > > Diagram out your topology and let me know exactly what you are
> > > > trying to accomplish and I can give you a better recommendation.
> > > >
> > > >
> > > > HTH,
> > > >
> > > > Brian McGahan, CCIE #8593 (R&S/SP)
> > > > bmcgahan@internetworkexpert.com
> > > >
> > > > Internetwork Expert, Inc.
> > > > http://www.InternetworkExpert.com
> > > > Toll Free: 877-224-8987 x 705
> > > > Outside US: 775-826-4344 x 705
> > > > 24/7 Support: http://forum.internetworkexpert.com
> > > > Live Chat: http://www.internetworkexpert.com/chat/
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> > Behalf
> > > > Of
> > > > > Venkataramanaiah.R
> > > > > Sent: Monday, October 30, 2006 10:59 AM
> > > > > To: Brian McGahan
> > > > > Cc: ccielab@groupstudy.com
> > > > > Subject: Re: Proxy-Arp with two routers on a segment..
> > > > >
> > > > > Brian, Moreover, you suggestion will apply only if i am proxy
> > arping
> > > B
> > > > > from A and vice versa.. But when i arp any other subnets, both
> > > routers
> > > > > will have these routers..
> > > > >
> > > > > In any case, i think bill's understanding with this issue is
> > > correct.
> > > > > Routers seem to responding only to the connect hosts. (They
> verify
> > > > > source addresses before responding with MAC). However, in our
> > case,
> > > > > our legacy hosts, which uses same NIC for both subnets, never
> uses
> > > > > second subnet to ask for MAC. So always R1 responds..
> > > > >
> > > > >
> > > > >
> > > > > On 10/30/06, Venkataramanaiah. R <vramanaiah@gmail.com> wrote:
> > > > > > Brian, I like your advise, but i cannot do that, i want this
> > > > > > intercommunication to around via both routers..
> > > > > >
> > > > > > It is a strange topology that we are trying to build upon
> here,
> > > with
> > > > > > legacy telcom hosts. So bear with me for that ;-)
> > > > > >
> > > > > > thanks
> > > > > >
> > > > > >
> > > > > > On 10/30/06, Brian McGahan <bmcgahan@internetworkexpert.com>
> > > wrote:
> > > > > > > You will only reply with proxy-arp if you have a route to
> the
> > > > > requested
> > > > > > > host's subnet. Remove router 1's route to subnet 2 and
> remove
> > > > router
> > > > > > > 2's route to subnet 1 and you will see the desired behavior.
> > > > > > >
> > > > > > >
> > > > > > > HTH,
> > > > > > >
> > > > > > > Brian McGahan, CCIE #8593 (R&S/SP)
> > > > > > > bmcgahan@internetworkexpert.com
> > > > > > >
> > > > > > > Internetwork Expert, Inc.
> > > > > > > http://www.InternetworkExpert.com
> > > > > > > Toll Free: 877-224-8987 x 705
> > > > > > > Outside US: 775-826-4344 x 705
> > > > > > > 24/7 Support: http://forum.internetworkexpert.com
> > > > > > > Live Chat: http://www.internetworkexpert.com/chat/
> > > > > > >
> > > > > > >
> > > > > > > > -----Original Message-----
> > > > > > > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]
> > On
> > > > Behalf
> > > > > > > Of
> > > > > > > > Venkataramanaiah.R
> > > > > > > > Sent: Saturday, October 28, 2006 1:09 PM
> > > > > > > > To: ccielab@groupstudy.com
> > > > > > > > Subject: Proxy-Arp with two routers on a segment..
> > > > > > > >
> > > > > > > > I have a requirement where there will be two routers on
> the
> > > same
> > > > > > > > segment supporting two different subnets... The segments
> > have
> > > > hosts
> > > > > > > > belonging to both these subnets..
> > > > > > > >
> > > > > > > > I want to enforce the following..
> > > > > > > >
> > > > > > > > Router 1 must respond to proxy-arp request only from hosts
> > > > belonging
> > > > > > > > to Subnet 1.
> > > > > > > >
> > > > > > > > Router 2 must respond to proxy-arp request only from hosts
> > > > belonging
> > > > > > > > to Subnet 2.
> > > > > > > >
> > > > > > > > Is there a way out..? I cant think of any way to achieve
> > > this,
> > > > so
> > > > > > > > thought i will ask the experts :-)
> > > > > > > >
> > > > > > > >
> > > > > > > > Regards
> > > > > > > > -Venkat
> > > > > > > >
> > > > > > > >
> > > > > > >
> > > > >
> > > >
> > >
> >
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