From: Richard Dumoulin (richard.dumoulin@vanco.es)
Date: Sun Jul 18 2004 - 18:44:42 GMT-3
For me a default-gateway is a routing function but in the management plane.
It is just used for when you need to manage the L2 switch from outside the
local network. Another thing is when the switch forwards in the data plane
...
--Richard
-----Original Message-----
From: Kenneth Wygand [mailto:KWygand@customonline.com]
Sent: domingo, 18 de julio de 2004 23:30
To: Lord, Chris; Brian McGahan; Alexander Arsenyev (GU/ETL);
ccielab@groupstudy.com
Subject: RE: 3550 COnnectivity
Chris,
Setting an IP default gateway is in no way a routing function. It's simply
a way to tell a layer-2-aware node to which local address to send
off-network packets. If the restriction is simply "no static routes", then
you can still use your IP default-gateway command.
It is recommended to use the "ip default-gateway" command to provide access
to any device that is not internally routing, and the 3550 with "no ip
routing" (which is default) is no different. However, you are correct in
that it doesn't hurt to ask the proctor. I wouldn't, however, assume arp
with proxy-arp on your remote routers is an acceptable solution to full
reachability.
Remember also, the lab is results-based. If they say you have to provide
full connectivity without using "ip default-gateway", just test it! If it
works, the points are yours! :)
Kenneth E. Wygand
Systems Engineer, Project Services
CISSP #37102, CCNP, CCDP, ACSP, Cisco IPT Design Specialist, MCP, CNA,
Network+, A+
Custom Computer Specialists, Inc.
"The only unattainable goal is the one not attempted." -Anonymous
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Lord, Chris
Sent: Sunday, July 18, 2004 4:10 PM
To: Brian McGahan; Alexander Arsenyev (GU/ETL); ccielab@groupstudy.com
Subject: RE: 3550 COnnectivity
As always, thanks to everyone for the interesting material in your postings.
I'm still left wondering slightly, what the answer to my original question
is though?
Trying to sum this all up, it seems that "full connectivity" will be
achieved by default through arp and proxy-arp, assuming that the scenario
does not also instruct you to turn-off proxy-arp on the connected router. In
the event that proxy-arp is disabled, then the use of "ip default-gateway"
seems permissible under the general rules, but it would be wise to check
with the proctor before making this assumption! If he/she says that you
can't use it then NAT is a possible alternative.
I think I get it :)
Thx,
Chris.
-----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
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
> 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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> > of
> > Lorien plc.
> >
> > Thank you for your co-operation.
> >
**********************************************************************
> >
> >
>
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