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New Member

Decnet bridging

Hello.

My client have a flat network ( LAN , about 700 users , 100 printers,100 servers , protocols are IP and Decnet ) .That will be separated to 12 vlans. The issue is a decnet traffic between vlans . How can i configure it ? Bridging ? IRB ? What is recomended ?

P.S. I cannot change Decnet addresses on computers ,so decnet routing is not relevant , i think.

Please advise.Thank you.

4 REPLIES

Re: Decnet bridging

When you introduce bridging you will lose the advantage of broadcast limitation. Your network will not perform well, probably even worse than now.

The best solution would be to put all DEC-net machines in one vlan.

This can be implemented without changing the DEcnet configuration.

Regards,

Leo

New Member

Re: Decnet bridging

Not so. If you do fallback bridging, the router will only bridge traffic that it isn't configured to route. So in this cast IP broadcasts will still be limited to a VLAN.

Other protocols can be filtered and/or otherwise dropped, depending on hardware platform etc.

-A

Gold

Re: Decnet bridging

Leo and Asbjoern have given you both sides of the issue: either separate all your DECnet onto its own VLAN, or have DECnet on every VLAN, and bridge it. Both methods work.

I have run into this problem twice: first, several years ago with a K-12 school system; and more recently, with a health care system. I used the approach that Asbjoern described, and applied an Ethernet type code access-list to filter out everything but DEC protocols from bridging.

Here are the command lines I used for the health care system. (I'm leaving out the IPX routing information to save space.) From inside config term,

bridge 1 protocol ieee

access-list 200 permit 0x6000 0x000F

access-list 200 deny 0x0000 0xFFFF

interface Vlan16

ip address 172.16.0.1 255.255.0.0

bridge-group 1

bridge-group 1 input-type list 200

interface Vlan17

ip address 172.17.0.1 255.255.0.0

bridge-group 1

bridge-group 1 input-type list 200

interface Vlan18

ip address 172.18.0.1 255.255.0.0

bridge-group 1

bridge-group 1 input-type list 200

interface Vlan19

ip address 172.19.0.1 255.255.0.0

bridge-group 1

bridge-group 1 input-type list 200

The first access-list 200 line permits a masked-out block of DEC protocols with consecutive Ethernet type codes from 0x6000, through 0x600F; this includes 0x6003 DECnet Phase IV, and 0x6004 DEC LAT. I suppose if you wanted to just permit DECnet traffic only, you could use the following first line instead:

access-list 200 permit 0x6003 0x0000

The second line in access-list 200 is the implicit "deny", stated explicitly. It's not really necessary, I just put it in so you know it's there. It blocks all other non-DEC, non-routed protocols from being bridged.

On the VLAN interfaces, "bridge-group 1" applies the bridge to the interface; and "bridge-group 1 input-type-list 200" applies the access-list to bridge-eligible traffic, catching it inbound to the router or multilayer switch interface from the VLAN and passing it through to the other interfaces only if it's DEC-type traffic.

Hope that helps.

New Member

Re: Decnet bridging

On a somewhat related note, here's a small pop quiz:

Q: What is the fastest way of stopping AppleTalk and IPX from being bridged, when you do fallback bridging?

A: 'ipx routing' + 'apple routing' in global config mode.

-A

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