From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Sun Jul 18 2004 - 04:31:08 GMT-3
When bridging IP it will ARP for everything (same with the
routers if you turn ip routing off). If you're routing IP you'll only
ARP for destinations that you have a route to. If by changing the mask
on a connected interface you encompass the destination in the connected
network it will ARP for it. Assuming the device on the other end
supports proxy-arp transmission will be successful. It's a fun exercise
in routing logic.
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
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> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Alexander Arsenyev (GU/ETL)
> Sent: Sunday, July 18, 2004 2:20 AM
> To: ccielab@groupstudy.com
> Subject: RE: 3550 COnnectivity
>
> I believe that Cat3550 will ARP for "everything" IF IP address/netmask
> combination
> on VLAN interface covers that "everything". That's why sometimes it's
> important
> to trick Cat3550 into thinking that "everything" is directly
connected,
> see
> my earlier post
> http://www.groupstudy.com/archives/ccielab/200406/msg01843.html
>
> HTH,
> Cheers
> Alex
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Brian McGahan
> Sent: 18 July 2004 01:29
> To: Kenneth Wygand; Mike Calhoon; Lord, Chris; ccielab@groupstudy.com
> Subject: RE: 3550 COnnectivity
>
>
> Ken,
>
> Your statements are true to a degree. Technically the 3550 is
> not using proxy-arp. Instead, it is just ARPing for everything. It
is
> the router that responds on behalf of the destination that is being
> ARPed for (hence proxy-arp).
>
> I only mention this point because it is the router on the
> attached segment that must be running proxy-arp, and not the switch
> itself.
>
>
> HTH,
>
> Brian McGahan, CCIE #8593
> 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
> > Kenneth Wygand
> > Sent: Saturday, July 17, 2004 5:23 PM
> > To: Mike Calhoon; Lord, Chris; ccielab@groupstudy.com
> > Subject: RE: 3550 COnnectivity
> >
> > Mike,
> >
> > Without specifying the "ip default-gateway", your 3550 will default
to
> > using proxy-arp to resolve your IP addresses to MAC addresses. If
> your
> > attached router (on the VLAN where your switch's IP address is)
> supports
> > proxy-arp, it will resolve and your ping will succeed.
> >
> > You should have entries if you do a "show arp" when using proxy-arp,
> but I
> > don't believe those entries will exist when crossing VLANs if you
have
> a
> > default gateway configured (just your default gateway will be in
your
> > local arp table).
> >
> > If you can, try it out both ways and post your outputs! :)
> >
> > Hope this helps,
> > Ken
> >
> > ________________________________
> >
> > From: nobody@groupstudy.com on behalf of Mike Calhoon
> > Sent: Sat 7/17/2004 6:18 PM
> > To: 'Lord, Chris'; ccielab@groupstudy.com
> > Subject: RE: 3550 COnnectivity
> >
> >
> >
> > Chris,
> >
> > I have wondered the same thing lately. I have found that as long
as
> the
> > rest of my routers have the route to the VLAN installed, I can ping
> the ip
> > on the switch without having to add "ip default-gateway", ip
routing,
> or
> > anything else to it. So full connectivity is being reached, but I
am
> > wondering if I should be adding "ip default-gateway" or anything
extra
> to
> > the switch.
> >
> >
> > Thanks,
> > Mike
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> > Lord, Chris
> > Sent: Saturday, July 17, 2004 5:03 PM
> > To: ccielab@groupstudy.com
> > Subject: 3550 COnnectivity
> >
> > Please could I ask for some opinions.......
> >
> > A lot of practice lab scenarios state standard assumptions such as
"do
> not
> > use static or default routes on any router, etc" and "full
> connectivity
> > must
> > be attained, etc". Suppose we met this in the real lab, my question
is
> > this... if one of the switches has a vlan interface with an ip
address
> > assigned to it then I assume the pod should be able to ping it and
> > vica-versa. If the switch is not running an IGP, is the use of "ip
> > default-gateway" permissible or does this break the rules?
> >
> > If you can't use "ip default-gateway" do you think configuring irdp
on
> the
> > attached router in the switch's management vlan would be a good
> > alternative?
> >
> > thx in anticipation,
> >
> > Chris.
> >
> >
> >
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Please
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> views
> > contained in this email are those of the author and not necessarily
> those
> > of
> > Lorien plc.
> >
> > Thank you for your co-operation.
> >
**********************************************************************
> >
> >
>
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