Dot1q Tunneling Benefits/Disadvantages

Unanswered Question
Jun 23rd, 2010

Hi, we are planning on replacing individual optical links between 2 of our sites with a couple of 10Gb optical links and than using a LAN switch to carve out that 10Gb into individual links for different environments that require a link between 2 sites. The switches used to host the 10Gb link are 6500's. I can see why a service provider might want to do this for various customers  however in this case it just seems that dot1q tunneling will be adding  the extra configs and not a lot of benefits.

1. Are there any benefit to using dot1q tunneling in this scenario as opposed to just using normal access vlan's for each link.

2. Are there any restrictions with the type of traffic that can be sent across a dot1q tunnel (mcast etc).

3. Are there any disadvantages to using dot1q in this scenario

I would appreciate any feedback on the above scenario and if anyone has any suggestions besides using MPLS which is not an option at this time. Thx for your help.

I have this problem too.
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Giuseppe Larosa Thu, 06/24/2010 - 06:05

Hello Vdadleney,

even if they are only two sites, by using 802.1Q in Q you get the capability to implement VRF lite by adding an internal vlan when needed with no changes on provider side.

Another possible advantage is that if you need to extend specific vlans over the two sites you can do it (this is the original use for it)

The only price to pay is the increased overhead : provider devices need to be able to handle frames with an additional 4 bytes 802.1Q tag. (two tags)

Nowdays provider can give a link with very high mtu from the begining so the MTU test is recommended just to check that everything is fine.

multicast traffic can be used but IGMP snooping capabilities can be somewhat limited but this is a service provider issue that doesn't apply until there are only two sites.

From SP's point of view all traffic travels in the external vlan-id between the two locations.

QoS marking should also be supported with external 802.1Q CoS bits copied from inner 802.1Q. This is another aspect to be investigated with the provider. I would ask about this aspect to them.

Hope to help

Giuseppe

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