From: John Moor (johmoor@gmail.com)
Date: Tue Oct 09 2007 - 16:38:28 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 10/9/07, John Moor <johmoor@gmail.com> wrote:
>
> 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 10/9/07, Guy Sherr <gsherr@gmail.com> wrote:
> >
> > Think about this. The only way for sw2 to be able to forward between
> > 30.30.30.2
> > and 50.50.50.2 is if sw2 is under the impression that they are on the
> > same vlan
> > (unless you have an IP route in sw2; I am assuming this at L2 and not
> > L3).
> >
> > Dot1q does not tag the native vlan unless you tell it to. If you have
> > native untagged
> > and make the sw2->sw1 trunk native vlan 50, then (obviously) traffic
> > without a tag
> > is "understood to be on vlan 50." However, if sw1 has vlan 30
> > configured native, then
> > it will be "understanding" those untagged frames on the trunk to be on
> > vlan 30.
> >
> > Are you getting a vlan mismatch maybe?
> >
> > On 10/8/07, John Moor <johmoor@gmail.com > wrote:
> > >
> > > 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.
> > >
> > > _______________________________________________________________________
> > >
> > > Subscription information may be found at:
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> > >
> >
> >
> >
> > --
> > "Whatever you do will be insignificant, but it is vitally important that
> > you do it." - Gandhi
This archive was generated by hypermail 2.1.4 : Fri Nov 16 2007 - 13:11:13 ART