From: John Moor (johmoor@gmail.com)
Date: Tue Oct 09 2007 - 16:39:25 ART
to guys: No everything is configured just as simple as I described. No
errors in the configuration. IP proxy arp is not explicitly configured but
probably yes it is enabled by default.
Let's look again into the topology
sw1-vlan30-------vlan30-sw2-vlan50------------------vlan50--sw3
Between sw1,sw2 and sw3 is just a simple dot1q trunk.
Configuration:
sw1-vlan30: 30.30.30.2
sw2-vlan50: 30.30.30.1
sw2-vlan50: 50.50.50.1
sw3-vlan50: 50.50.50.2
On all trunks configuration is really very simple:
switchport
switchport trunk enc dot1q
sw mode trunk
on vlans like:
vlan 30
ip address 30.30.30.2
switch 2.
vlan 30
ip address 30.30.30.1
vlan 50
ip address 50.50.50.1
...
sw1 vlan 30 int can bing vlan 3 vlan 50 int withou any default gateway or
routing configured. Proxy arp.. yes maybe.
But question is still the same:
sw3 can receive proxy arp reply from sw2 but how can it forward packet
without having any routing entry in its table? The PC can actually send a
packet out it's interface without default gateway configured if it receives
proxy arp reply. Maybe it is the same with the switch?
Any thoughts?
P.S http://www.tildefrugal.net/tech/arp.php look here what PC do if it don't
have default-gateway configured...
On 10/8/07, Joseph Brunner <joe@affirmedsystems.com> wrote:
>
> Proxy arp is known for this "interesting behavior"
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> John
> Moor
> Sent: Monday, October 08, 2007 12:57 PM
> To: Cisco certification
> Subject: interesting behaviour of the switches
>
> Hello, guys!
> I have mentioned interesting behaviour. Could you pleas confirm this or
> tell
> that this is incorrect?
> sw1-vlan30-------vlan30-sw2-vlan50------------------vlan50--sw3
>
> Between sw1,sw2 and sw3 is just a simple dot1q trunk.
> Configuration:
> sw1-vlan30: 30.30.30.2
> sw2-vlan50: 30.30.30.1
> sw2-vlan50: 50.50.50.1
> sw3-vlan50: 50.50.50.2
>
> I can ping from 50.50.50.2 to 30.30.30.2 even without configuring
> default-gateway on sw 3. I assume that it happenes because when sw3
> doesn't
> know the route it just broadcasts the ip packet and the same does sw1 in
> opposite to the router.
>
> Is it correct? Or there is some other explanation of this. Thank you.
>
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This archive was generated by hypermail 2.1.4 : Fri Nov 16 2007 - 13:11:13 ART