I worked through some Frame Relay scenarios last weekend and used tunnel
interfaces to switch frames between three routers on an Ethernet segment
(representing a core). I had several PVC's up but ran into problems
when I tried
the following:
R1(s0 dte)----(s0 dce)R2(tun 0)----(tun 0)R3(s0 nni)----(s1 nni)R2(tun
1)----(tun
1)R4(s0 dce)----(s0 dte)R5
You can see the loop between R2 and R3. All of the DLCI's were unique
on each
router and everything looked like it should work, but no luck. Although
PVC's
across these devices that didn't create a loop like this worked fine.
If DLCI's
are locally significant, it shouldn't matter that the PVC crossed the
same router
twice.
Tighe
Chuck Larrieu wrote:
> I've been saving this one for a while also. Originally I was going to write
> this off as another one of those questions. Then I got to wondering about
> the genesis of it. Did a bit of research. Interesting.
>
> http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/wan_
> c/wcdfrely.htm#xtocid15531103
> watch this word wrap...
>
> the short answer to Mr. Ozbourne's question is yes it can be done. The
> question itself indicates a bit of uncertainty. I know when I was
> considering it, and poking around CCO, my thought was that tunnels are layer
> three and frame relay is layer two and therefore no it can't be done.
>
> But Cisco continues to be full of surprises. The IOS is very rich in
> features that allow one to do a wide variety of things in any number of
> ways. Sometimes I'm too dense to understand the reasons behind the
> possibilities.....
>
> So....
>
> 1) One may use Cisco routers as frame relay switches.
> 2) One may use Cisco routers as X.25 switches
> 3) One may tunnel frame relay and X.25 and SNA and any number of other
> things over IP networks.
>
> For example, if one were migrating an enterprise to an IP only backbone, but
> one had an extensive embedded base of whatever, one would take advantage of
> the rich Cisco feature set to make this possible. So I have a New York
> office, a Los Angeles office, and Fargo office. I want a high speed core,
> using DS3. Can't do X.25 over DS3, so I have to fake out my existing X.25
> network by making my Cisco edge routers X.25 switches and tunnelingX.25
> across the backbone. OK I understand the theory. Same for SNA. But for
> frame-relay I'm scratching my head.
>
> Network-----frame_relay----router------IP_Core_Network--------router-----fra
> me-relay-----network
>
> Possibly there might be some advantage to create such tunnels so that
> routers are but one hop away from eachother? Possibly I am looking at this
> the wrong way, and the issue is one of a large organization with a bunch of
> Stratacom switches in various locations, and wanting to take advantage of a
> high speed core somehow? I get the feeling that this feature exists as a
> means of helping transition from one structure to another. I just don't
> understand the structures involved.
>
> Chuck
>
> P.S. Yes Dave, your configurations will work. They are almost identical to
> configurations found in the link above.
>
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Dave
> Ozbourne
> Sent: Thursday, July 13, 2000 8:48 PM
> To: [EMAIL PROTECTED]
> Subject: 2 2501's as a frame relay switch - Once and For All
>
> Searched the archives on Groupstudy and found varying answers on the
> follwoing config, for 2 2501's connecting through a tunnel to simulate
> a frame relay switch.
> Does it work yes or no?
> Thanks
>
> Cisco 2501 # 1
> !
> version 11.2
> service udp-small-servers
> service tcp-small-servers
> !
> hostname r1
> !
> !
> frame-relay switching
> !
> interface Tunnel0
> no ip address
> tunnel source Ethernet0
> tunnel destination 192.168.1.1
> !
> interface Ethernet0
> ip address 192.168.1.2 255.255.255.0
> !
> interface Serial0
> no ip address
> encapsulation frame-relay
> clockrate 1000000
> frame-relay lmi-type ansi
> frame-relay intf-type dce
> frame-relay route 112 interface Serial1 211
> frame-relay route 113 interface Tunnel0 311
> frame-relay route 114 interface Tunnel0 411
> !
> interface Serial1
> no ip address
> encapsulation frame-relay
> clockrate 1000000
> frame-relay lmi-type ansi
> frame-relay intf-type dce
> frame-relay route 211 interface Serial0 112
> !
> no ip classless
> !
> line con 0
> line aux 0
> line vty 0 4
> login
> !
> end
>
> Cisco 2501 # 2
> !
> version 11.2
> no service password-encryption
> no service udp-small-servers
> no service tcp-small-servers
> !
> hostname r2
> !
> !
> frame-relay switching
> !
> interface Tunnel0
> no ip address
> tunnel source Ethernet0
> tunnel destination 192.168.1.2
> !
> interface Ethernet0
> ip address 192.168.1.1 255.255.255.0
> !
> interface Serial0
> no ip address
> encapsulation frame-relay
> clockrate 1000000
> frame-relay lmi-type ansi
> frame-relay intf-type dce
> frame-relay route 311 interface Tunnel0 113
> !
> interface Serial1
> no ip address
> encapsulation frame-relay
> clockrate 1000000
> frame-relay lmi-type ansi
> frame-relay intf-type dce
> frame-relay route 411 interface Tunnel0 114
> !
> no ip classless
> !
> !
> line con 0
> line aux 0
> line vty 0 4
> login
> !
> end
>
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--
Tighe Kuykendall
Senior Systems Engineer
[EMAIL PROTECTED]
828.251.3204
Prism Technology Resources, Inc.
223 Haywood Street
Asheville, NC 28801
http://www.Prism-Tech.com
--
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