Re: LAT protocol implementation with Catalyst Switches.

hillolnath · ‎09-08-2005

I have CS-6509 and CS-2950G-EI catalyst switches in my network.

I also have a DEC ( Digital equip.Corp) 900TM HUb/repeater connected to one of the port of 6509 switch.

The reson for the DEC hub is because we have some serail devices and few VT100 terminals which are connected to the DEC hub ports and run DEC properiety protocol called LAT(local Area transport).The DEC Hub in turn connects to a Unix Box. Both the DEC Hub and unix box understands LAT.

My issue is :

1. I want to move these serial/VT 100 devices from the DEC hub to cisco 2950 or 6509 switches .

2. how do i implement LAT on cisco switches .Do i need special IOS version for 2950 /6509.

3.The config on the DEc Hub ports are preety simple more like Com port config.

4. Is there any special links in cisco website about configuring LAT .

please advice.

Thanks.

Georg Pauwen · ‎09-08-2005

Hello,

there is not a whole lot of information available on LAT. As for the Cisco switches, you should be ok as long as the LAT terminals are in the same VLAN. The problem is when Layer 3 routing comes into play. The MSFC on the Catalyst 6500 does not appear to support LAT at all, most routers do, you need an IOS version like Enterprise Plus.

Is there a need for routing, or do you just want to connect the terminals to the Cisco switches ?

Regards,

GP

hillolnath · ‎09-08-2005

Hello GP,

Thanks for your reply.Actually my devices are connected to a 2950 access switch(layer2), which in turn connects to core switch (6509).

Currently all devices are in VLAN1. However in future, if i have to do the following, then what would be the config on the switch port and 6509.

1.If i keep the source serial device and destination Unix device in same Vlan.

2.If i have to do routing between diffrent vlans of source and destination device.

3.If all devices are in VLAN 1, what would be the commands for configuration of ports.

Is there any particular requirement of IOS for 2950 switch. what would be the actual commands on switch ports.

Thanks.

michael_davis · ‎09-09-2005

Strictly speaking, and at the core of this issue, no routers support LAT because it includes no L3 information. At best, it can be bridged. It can also be encapsulated in IP, then transported over an IP network, then de-capsulated. DLSW would be useful for doing so.

The MSFC does support bridging of non-routable protocols between vlans, as alonzo-garza pointed out. His config routes IP traffic, and bridges non-routable, including SNA, LAT, Netbeuei, etc, across vlans.

I'm saying this, not to mince words, but to point out the following:

If both hub and server are on the same vlan, and the switches are interconnected via trunk, but there is no communication, then the trunk interface or configuration is to blame for the failure.

If hillolnath would like to post configs for your switches, it may be helpful.

We'd want to verify vlans, vtp mode/domain/passwords/versions, native vlan, trunking mode, trunking encapsulation, etc for both switches.

Also, I mentioned changing transports earlier, but I recognize that this might not be possible. Indeed, if the trunk is failing, IP won't help either. :-)

alonzo-garza · ‎09-08-2005

Hi, I work in a refinery and I am VERY familiar with the LAT issue you have. I am running 4506's which have about 10 vlans. The previous response from the other gentlemen was correct. Keep your UNIX boxes and those LAT terminals on the SAME VLAN / subnet and you will communicate just fine. If for some reason you can't keep them on the same vlan than simply add the following lines to your router that seperates them....1st you will globally define the bridge 1 protocol and 2nd you will define which interface belongs to that bridge group, of course this is not a very good design for broadcasts because all your doing at this point is turning your router into a Brouter or bridge/router.

1st.add this global command 'bridge 1 protocol ieee'

2nd add this into interface mode of let's say int fa0/0 'bridge group 1'

example...

interface FastEthernet0/0

description bridged port for LAT

ip address 1.20.5.1 255.255.255.0

no ip redirects

no ip proxy-arp

duplex auto

speed auto

no cdp enable

bridge-group 1

let me know if this helps,

-Alonzo

hillolnath · ‎09-08-2005

Hi Alonzo,

Thanks for you advice.

However let me tell you that since this is a new site, all my LAT devices and Unix box are in VLAN 1 with default port setting and layer 2 switching. The serial LAT deive is connected to a 2950 switch port and Unix box to a ethernet port on the 6509.Both switch connects via a fibre link.

However this connectivity dont work and the serial device is not able to ping the Unix box.

So what are the comands that i need to put on the fast ethernet ports on both switch. IS any other global commands required.?

Please have a look into the current DEC settings for the server port ( Unix device connected ) and the Port 29 settings for the VT 100 terminal.

michael_davis · ‎09-08-2005

Just wanted to mention the 900TM supports LAT, Telnet, and SLIP. If possible, you might consider telnet to eliminate the bridging issues mentioned by others in this thread, and especially since you're communicating with a Unix box.

Anyway, it sounds like a trunking problem.

Take a look at the following and verify that you've got your trunks set up correctly:

http://www.cisco.com/en/US/customer/tech/tk389/tk213/technologies_configuration_example09186a0080094bc5.shtml

Also, spanning-tree portfast may well be your friend here on server and 900TM ports...

HTH

alonzo-garza · ‎09-09-2005

I read the following thread by michael davis and he seems to be right on. I would see if you can set up a tcp listener port on your dec server. Also, since your serial devices and your unix server hangs off of VLAN 1, double check to make sure your not pruning VLAN 1 and it is in fact part of your dot1q trunk.

I'm using a DEC 700 Terminal Server, I've included it's telnet listener configs so you can check it out.