Cisco Router command "encapsulation dot1q 1 native"

[Abdulhadi]

Cisco Router command "encapsulation dot1q 1 native":

The "encapsulation dot1Q 1 native" command is used on cisco router to
a associate a subinterface to a VLAN, configured as Native on the
Switch. On the switch, if you have a native VLAN other than VLAN1, on
the router, configure the same VLAN to be the native VLAN.

The "encapsulation dot1Q 1 native" command was added in Cisco IOS
version 12.1(3)T. If you are using an earlier version of Cisco IOS,
the IP address for VLAN1 (Native VLAN) is configured on the main
interface, and no encapsulation for VLAN1(Native VLAN) will be done
under the sub-interface.

While configuring 802.1Q trunking it is very important to match the
native VLAN across the link. In the Cisco IOS software versions
earlier than 12.1(3)T, you cannot define the native VLAN explicitly,
as the encapsulation dot1Q 1 native command under the sub-interface is
not available. In the earlier Cisco IOS versions, it is important to
configure the native VLAN-Interface not as a sub-interface, for
example VLAN1. If configured wrong, the router would expect a tag
dot1q frame on VLAN1 and the switch is not expecting a tag on VLAN1.
As a result, no traffic will pass between VLAN1 on the switch and the
router. In these situations always put the configuration for the
native VLAN under the main interface and on the trunk create
subinterface for all other VLANS.



--
Abdul Hadi
------------------------------------------------------------
Knowledge is knowing a fact.
Wisdom is what to do with that fact.
B.J. Palmer
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[Andrei Stingaci]

Thank you!

[fai...@live.ca]

I have a network in my home office that includes Windows PCs, a Ubuntu file server, a Fedora backup server and a VoIP appliance.

The VoIP box is actually a 1-port D-Link router configured by Primus to allow a regular telephone to use their Internet TalkBroadBand service.

The WAN port on my VoIP router  plugs into a QoS-configured LAN port on my Linksys WRT300N router.

I have done that for years so I can easily remove the Primus box and carry it with me to client sites and/or into hotel rooms.

Callers just think they have reached me in my office when they call or see my incoming Caller ID.

 

I was having technical difficulties with my VoIP phone so I contacted Primus.

Their instructions were to plug a cable directly between a PC and the LAN port of the Primus box, and power cycle both Primus box and PC.

Then I was to point a browser to 192.168.15.1, sign on and reset the router to factory defaults.

That would have required me to crawl around behind shelves and under desks to figure out which cable needed to be pulled, moved and put back later.

That seemed like a real waste of my time.

 

Instead, I decided to approach the problem another way.

I defined a shared port eth0:0 with a gateway of 192.168.15.1 on my Fedora server and set that interface up to accept DHCP .

That gave me two interfaces on the single physical interface, with each one asking a different DHCP server for an IP address.

I plugged a cable between the Primus LAN port and the switch that normally handles my local network of 10.20.30.0.

I confirmed that I could ping both my Linksys router at 10.20.30.1 and my Primus router at 192.168.15.1.

Then I connected my browser to 192.168.15.1 and reset my Primus box back to factory settings.

 

I thought you might be interested in at least one practical application for one of the Linux labs we did.

Hope you are all having a good mini-vacation.

See you on Tuesday.

 

Fairch

 

 

 

[Andrei Stingaci]

Nice, Linux really rules) Besides, do we have a quiz on chapter 7 on Tuesday (I didn't attend Thursday's class ...)?
Andrei

2010/9/4 <fai...@live.ca>