Topology question

[jrmoraes77]

I´m working in a network design that requires some layers of routers.

1. Access - routers responsible for WAN connection.

2. DLSw+ termination - routers responsible for receive and terminate de DLSw+ connections.

3. SNA connection - routers responsible for connect to mainframes with CIP interface.

Between layer 1 and 2 I have a Gigabit bus made with some switches. But, between layer 2 and 3 I have some doubt, in all samples provided by Cisco this connection is allways made through a Token Ring interface, is possible make this connections over a Gigabit or FastEthernet ? If yes, where I can find some sample ?

Best Regards

[dixho]

To answer your question, yes, you can connect the DLSw termination router and the CIP/SNA connection router by a Gigabit or FastEthernet router. You need to run transparent bridging on the Gigabit or FastEthernet interface. Then, use dlsw bridge-group command as shown in the following URL:

http://www.cisco.com/warp/customer/697/3.html

Then, you enable SR/TLB on the CIP router, similar to the following URL:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fibm_c/bcfpart2/bcfcmpc.htm#1004041

However, you may run into MTU problems. Well, in SNA's term, I should say RU size problem.CIP is considered a token ring to VTAM (i.e. lan tokenring under CPA/CIP interface). VTAM or PU2.1 may send a packet larger than 1500 bytes. Transparent bridging just drops them.

I suggest you to consider the followings:

1. terminate DLSw on the CIP router

2. use a token ring or TRISL between layer 2 and 3

3. use SNASw on the remote router. Connect the remote router to the host by HPR/IP

[jrmoraes77]

To fix the problem of RU size is possible enable jumbo frames on routers and LAN switches ?

Regards

[dixho]

No. Most implementations uses LLC2 (i.e. 802.2) frame format. The third field is the length of the packet. If the length of the packet is greater than 1500 bytes, all ethernet devices will treat the packet as a DIX packet. Thus, the SNA device will not decode the packet properly.

IOS drops the packet on the bridge code. The packet does not even reach the outgoing interface.

[jrmoraes77]

You can provide some URL with sample of TRISL configuration applied to this environment ?

Thank you for your assistance.

[dixho]

Please configure SRB on TRISL, as shown in the following URL:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fibm_c/bcfpart1/bcfvlan.htm#1002844

Then, configure source-bridge ring-group, dlsw local-peer, and dlsw remote-peer .

[jrmoraes77]

All examples in this URL are based on physical token ring interface. I will need this interface to make this environment working ?

Thank's

[dixho · Accepted solution]

I copy the example I meant in my last posting:

interface fastethernet4/0.1

ip address 5.5.5.1 255.255.255.0

encapsulation tr-isl trbrf-vlan 999 bridge-num 14

multiring trcrf-vlan 200 ring 100

multiring all

!

interface fastethernet4/0.2

ip address 4.4.4.1 255.255.255.0

encapsulation tr-isl trbrf-vlan 998 bridge-num 13

multiring trcrf-vlan 300 ring 101

multiring all

From the above, TRISL is configured on two FASTETHERNET SUBINTERFACES, not physical token ring interfaces. Does this address your concerns?

[jrmoraes77]

Yes, I'm sorry this questions, but I'm new this environment.

Thank you very mutch for your assistance.