From: Alexander Arsenyev (GU/ETL) (alexander.arsenyev@ericsson.com)
Date: Sun Jul 18 2004 - 04:37:32 GMT-3
So will Cat3550 with one VLAN interface with IP address, say 10.0.0.1/16, ip routing disabled, ip default-gateway not configured, ARP for an IP address 11.0.0.1? I'm pretty much sure it won't do ARP with "ip routing" statement in config.
Don't have a Cat3550 to test it now :-)
Cheers
Alex
-----Original Message-----
From: Brian McGahan [mailto:bmcgahan@internetworkexpert.com]
Sent: 18 July 2004 08:31
To: Alexander Arsenyev (GU/ETL); ccielab@groupstudy.com
Subject: RE: 3550 COnnectivity
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.
http://www.InternetworkExpert.com
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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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> > of
> > Lorien plc.
> >
> > Thank you for your co-operation.
> >
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> >
> >
>
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