dslreports logo
site
 
    All Forums Hot Topics Gallery
spc

spacer




how-to block ads


Search Topic:
uniqs
2733
share rss forum feed


At1

@1.22.14.x

[CCNA] Inter VLAN Routing

If configuring sub-interfaces on a router with a switch,then inter VLAN Routing is also enable automatically....am i right???


nosx

join:2004-12-27
00000
kudos:5

Providing the hosts in each vlan use the appropriate routers subinterface IP for their gateway, yes. Traffic should be able to route from one subinterface to another when all connected to the same router.


HELLFIRE
Premium
join:2009-11-25
kudos:18
reply to At1

CCNA answer -- yes.

Production answer -- how many EVPs do you have riding on getting this working?

Regards



At1

@1.22.14.x

Can i configure sub-interfaces without inter vlan routing???Is it possible??Can anyone suggest any other methods??


sk1939
Premium
join:2010-10-23
Mclean, VA
kudos:10

The most common use for sub-interfaces is for inter-vlan routing, I can't really think of another reason to use it other wise. What is it that you are trying to do?


cramer
Premium
join:2007-04-10
Raleigh, NC
kudos:9
reply to At1

Can i configure sub-interfaces without inter vlan routing???

Sure. But what's the point. You'd have to turn off routing. (and before anyone gets any ideas, ethernet sub-interfaces cannot be bridged.)

Also, no. It is *NOT* automatic...

rtr1811(config)#int f1.1
rtr1811(config-subif)#ip address 192.168.1.1 255.255.255.0
% Configuring IP routing on a LAN subinterface is only allowed if that
subinterface is already configured as part of an IEEE 802.10, IEEE 802.1Q,
or ISL vLAN.

If *YOU* don't set the encap's to a vlan, it won't accept sub-int's. But otherwise, yes, sub-interfaces on ethernet must be in a vlan. At which point, it will route between them unless you have done something to prevent it. (i.e. a non-default setting.)

[as you should be learning in any Cisco training... Cisco Logic(TM) and the real world are very different things. Cisco would have you think there's a yes/no answer to every question. In reality, there are no yes/no Cisco questions.]

[*cough*VRF*cough*]

Network Guy
Premium
join:2000-08-25
New York
kudos:2

I'm reading through the ICDN2 book now, chapter 3. I'm looking forward to reading about VRF.

Setting subinterfaces on a router for every VLAN seems ineffective though. There's gotta be a better way.


aryoba
Premium,MVM
join:2002-08-22
kudos:4
reply to At1

said by At1 :

Can i configure sub-interfaces without inter vlan routing???Is it possible??Can anyone suggest any other methods??

If you are referring to sub-interfaces under Serial interfaces for (let's say) Frame Relay, then such Serial sub-interfaces are not necessary for inter-VLAN routing.

As cramer See Profile mentioned, Ethernet sub-interfaces on routers could be used for something like VRF. When you review the basics, creating Ethernet sub-interfaces is producing multiple broadcast domains which from Layer-2 perspective does not matter should those domains talk or even see each other.

HELLFIRE
Premium
join:2009-11-25
kudos:18
reply to At1

said by cramer:

Can i configure sub-interfaces without inter vlan routing???

Sure. But what's the point. You'd have to turn off routing.

I agree... kinda like drilling a hole in the wall for a door that does nothing...what's the point?

said by Network Guy:

Setting subinterfaces on a router for every VLAN seems ineffective though. There's gotta be a better way.

From an NA perspective, a multilayer switch. In a production environment... don't know if
one exists. If there is one, I don't see one in the environments I support.

Regards

aryoba
Premium,MVM
join:2002-08-22
kudos:4

said by HELLFIRE:

said by cramer:

said by Network Guy:

Setting subinterfaces on a router for every VLAN seems ineffective though. There's gotta be a better way.

From an NA perspective, a multilayer switch. In a production environment... don't know if
one exists. If there is one, I don't see one in the environments I support.

There are some places that has such "router-on-the-stick" design, where these place cannot afford Layer-3 switch as core switch. In fact hybrid Catalyst 6500 series has such design internally where the CatOS running the Layer-2 and the MSFC IOS running the Layer-3.

HELLFIRE
Premium
join:2009-11-25
kudos:18

// slaps forehead

Okay, forgot about that one aryoba. Whether that's a 'better way' I leave up to the supporter. CatOS has some
nice things about it, but having to switch constantly between two OSes to do your job wears you down.

Regards



FLengineer
CCNA, CEH, MCSA
Premium
join:2007-06-26
Leesburg, FL

The OP may be wanting a VLAN ACL but isn't sure what it's called. You could simply use a VLAN ACL to deny traffic between the VLANs if you don't want interVLAN routing.


aryoba
Premium,MVM
join:2002-08-22
kudos:4

said by FLengineer:

The OP may be wanting a VLAN ACL but isn't sure what it's called. You could simply use a VLAN ACL to deny traffic between the VLANs if you don't want interVLAN routing.

Another approach is simply not assigning IP address under the router sub-interface; so that the router is just splitting broadcast domains without the necessity of IP routing capability and without turning the whole router into a bridge.