Kara wrote:

Do the Cisco routers work for dumb terminals?  We are looking for a
cost-effective way to remove bridging from our network.  Currently, we have
dtcs at remote locations with a dtc manager centrally located which allows
dumb terminals to connect to any of our MPE or Unix systems.  Some options
we've considered were host-based dtc management or terminal servers.  I was
told that the only other option was to locate dtc managers at each site.
Then the bridging would only be on the segment between the dtc manager and
the dtc's, not on the whole network.  It's not currently a hot issue, but
will again soon, I'm sure.

Ideas?

Kara Strunk

------------------Reply separator----------------------

I've replied privately to 2 other similar messages over the past
couple of weeks. This time I decided to post it to the list for
anyone else who may also benefit from it.

Kara,

You have most everything you need already in place.  The only
remaining task is to configure bridging on the Cisco router(s).
Basically what you need to do is configure transparent bridging on
each router that needs to bridge packets.  This alone will bridge
your remote DTCs to the central site.  However, you may then
experience some performance problems.  To avoid this, create a MAC
address list on both the central router and the remote router(s).

The remote router's MAC address list should permit forwarding of
packets to and from the DTC (MAC address) on the LAN (Ethernet) port
of the Cisco router. It should also permit forwarding of packets to
and from specific server MAC addresses on the WAN (Serial) interface.
That is - the HP3000(s) and the DTC/Manager server at your central
site.

On the remote router configure "NO BRIDGE n ACQUIRE" (n is the bridge
environment number you assign to the bridge group) - otherwise the
router will acquire MAC addresses for every device on every network
known to the router and forward their packets over all network
connections. If you do a "show bridge <interface_name>", you will
probably see screen after screen of MAC addresses in the table. After
setting up the MAC table, only packets to/from the hosts defined in
the MAC list will be forwarded - all others will be discarded.

On the central router configure a MAC address table in much the same
way.  If you have multiple WAN interfaces or use subinterfaces,
create a MAC list entry or each of these - pointing to the MAC
address of the remote LAN's DTC. Likewise, create an entry for each
of the bridged services on the central LAN connection. If you have
multiple remote sites, you should configure those sites before
implementing these changes on your central router. After everything
is configured on the central router enter config mode and do a "NO
BRIDGE n ACQUIRE".

Below is an example of one of our remote Cisco router configs.  Note
- we use separate Frame Relay PVC's for IP and Bridging. However,
this should work just as well on a shared IP/Bridged PVC:

-----------------------------------------

!
version 11.2
service timestamps debug datetime msec localtime
service timestamps log datetime msec localtime
service password-encryption
service udp-small-servers
service tcp-small-servers
!
hostname gf_router
!
enable secret 5 xxxxxxxxxxxxxxxx
enable password 7 xxxxxxxxxxxxx
!
ip hp-host fcpl.fairfax.lib nnn.nnn.nnn.nnn
ip hp-host fcpl nnn.nnn.nnn.nnn
ip domain-name your.domain.name
ip name-server your.name.server
isdn switch-type basic-dms100
clock timezone EST -5
clock summer-time EDT recurring
!
interface Ethernet0
 description Great Falls Ethernet LAN
 ip address nnn.nnn.nnn.nnn nnn.nnn.nnn.nnn
 loopback
 priority-group 1
 bridge-group 1            (Turns on bridging for this interface)
!
interface Serial0
 description GF Circuit # 36.QGDQ.746758 to CH/Tech. Ops.
 no ip address
 encapsulation frame-relay
 priority-group 1
 frame-relay lmi-type ansi
!
interface Serial0.1 point-to-point
 description IP PVC mapped to CH/Tech. Ops DLCI 535
 ip address nnn.nnn.nnn.nnn nnn.nnn.nnn.nnn
 frame-relay interface-dlci 337
!
interface Serial0.2 point-to-point
 description IEEE STP PVC mapped to CH/Tech.Ops. DLCI 536
 frame-relay interface-dlci 338
 bridge-group 1           (Turns on bridging for this interface)
!
interface Serial1
 description Spare Serial Interface
 no ip address
 shutdown
!
interface BRI0
 no ip address
 shutdown
!
router eigrp 3333
 passive-interface Ethernet0
 network nnn.nnn.nnn.nnn
 network nnn.nnn.nnn.nnn
 no auto-summary
!
no ip classless
priority-list 1 protocol bridge high
snmp-server community public RO
snmp-server community fcpl RW
snmp-server community fcpl1 RW
snmp-server host nnn.nnn.nnn.nnn host_name
bridge 1 protocol ieee                    (Defines the bridge environment)
no bridge 1 acquire                       (The Cisco default is to "acquire")
bridge 1 address 0800.0970.1b3b forward Ethernet0         (remote DTC)
bridge 1 address 0800.09db.e15f forward Serial0.2 338     (central HP3000)
bridge 1 address 0800.0998.38df forward Serial0.2 338     (central HP3000)
bridge 1 address 0800.09c0.ca22 forward Serial0.2 338     (central DTC/Mgr.)
!
line con 0
 timeout 0 0
 password 7 xxxxxxxxxxxx
line aux 0
 transport input all
 rxspeed 2400
 txspeed 2400
 flowcontrol hardware
line vty 0 4
 password 7 xxxxxxxxxxxxx
 login
!
end

___________________________________________

Steve Barrett

    Steven P. Barrett    [log in to unmask]
    Systems Analyst
    Fairfax County Public Library     (703) 222-3132 - Voice
    Technical Operations Center       (703) 222-3135 - FAX
    4000 Stringfellow Rd.
    Chantilly, VA  20151

    --- The opinions expressed here are mine alone . ---

    If God had meant for us to have distributed systems, he
    would have put little brains in our hands and in our
    fingers.  (Unknown Author)