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problems with a stub network on Frame Relay network

By CG IT ·
Working with a client that has a private frame-relay network. While there are no issues with the frame-relay network, they are trying to connect the frame-relay network to the Internet via a stub network. The stub is off a 3640 at one of the sites using an ethernet connection from the 3640 to the perimeter router, then off to the internet. Everyone on the frame-relay network [all subnets] can ping the ethernet interface on the 3640, but they can not ping the DSL perimeter router. eg packets are dropped at the 3640 ethernet interface that connects to their DSL router [the stub network].

Here's a ip route table [RIP] from the 3640: Router#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route

Gateway of last resort is 192.168.X.X to network 0.0.0.0

172.16.0.0/24 is subnetted, 3 subnets
R 172.16.40.0 [120/1] via 172.16.20.2, 00:00:08, Serial0/0
R 172.16.30.0 [120/1] via 172.16.20.1, 00:00:09, Serial0/0
C 172.16.20.0 is directly connected, Serial0/0
173.55.0.0/16 is variably subnetted, 2 subnets, 2 masks
R 173.55.0.0/16 [120/3] via 172.16.20.2, 00:00:08, Serial0/0
R 173.55.107.0/24 [120/1] via 192.168.X.X, 00:00:16, Ethernet0/0
C 192.168.X.X/24 is directly connected, Ethernet0/0
S* 0.0.0.0/0 [1/0] via 192.168.X.X
is directly connected, Ethernet0/0

The 192.168.X.X directly connected to ethernet 0/0 is the stub network off to the DSL router. The DSL router has the 192.168.X.X subnet.

Note: you can ping yahoo from the 3640 ...


Here's the ip route table [RIP] from one of the sites :
Gateway of last resort is not set

172.16.0.0/24 is subnetted, 3 subnets
R 172.16.40.0 [120/1] via 172.16.20.2, 00:00:03, Serial0/0
C 172.16.30.0 is directly connected, FastEthernet0/0
C 172.16.20.0 is directly connected, Serial0/0
R 173.55.0.0/16 [120/3] via 172.16.20.2, 00:00:03, Serial0/0
R 192.168.X.X/24 [120/1] via 172.16.20.2, 00:00:03, Serial0/0
Router#


While the gateway hasn't been set at the site they can ping the 3640 ethernet interface via the frame-relay network.

They advised me they set the gateway to the DSL perimeter router 192.168.x.x [1 hop away] eg o.o.o.o = 192.168.x.x and that didn't work.

IP classless is running on all routers.

Any ideas why the stub network will not allow icmp ping from frame-relay sites to the perimeter router ?

note no ACLs on any router and no firewalls block icmp traffic. any host on any of the frame-relay sites can ping the ethernet interface on the 3640 which is the stub network and where the DSL perimeter router connect to. It appears that when icmp ping gets to the 3640 ethernet interface, it doesn't forward them to the DSL router rather drops the packets.

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All Answers

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A Stab in the dark

by NetMan1958 In reply to problems with a stub netw ...

Does the DSL router have routes to the 172.16.X.X networks? If it just has a defualt route then it must point to the ISP's network which will drop traffic destined for 172.16.X.X.

From the 3640 itself a ping will be sourced from 192.168.X.X which is connected to the DSL router so it will have a route back to the 3640.

If you ping from one of the 172.16.X.X devices, it's source IP will be 172.16.X.X and when the ping reaches the DSL router, if all it has is one default route and no specific routes back to the 172.16.X.X net, it will try to send them through the ISP.

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Yep they said the DSL router has

by CG IT In reply to A Stab in the dark

static routes created to the 172.16.X.X frame-relay network subnets....

but I'll have then run a ip route command to verify that in the DSL router that the 172.16.X.X networks show up in the route table.

Thanks Netman!!

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General Guess

by robo_dev In reply to problems with a stub netw ...

I'm no Cisco guru, and it's hard to understand the topology exactly without a Visio diagram, but are you using RIP for the stub router?

Most of the config examples I see are for EIGRP or OSPF for stub routers....or am I confused?

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They run god awful RIP on their network...

by CG IT In reply to General Guess

I think whoever first set it up probably didn't know Eigrp or OSPF.

Here's a diagram for you

Frame-relay switch with 8 Async ports at HQ

each site connects to 1 of the 8 Async ports and used frame-relay encapsulation. There is a frame-relay circuit between each site. The frame-relay switch simply moves frames around between each site. it's a completely closed network with no internet access.

someone go the idea at one of the sites to setup internet access via a DSL line they had, so they setup a stub network off their site router [which is a 3640] by running a cat 5 from an unused ethernet port on the 3640 to the DSL router/modem.

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Sorry that link to diagram did not work

by robo_dev In reply to They run god awful RIP on ...

I think that's huge clue that they did not know EIGRP or OSPF, because one reason Cisco recommends those protocols is because it's tricky to get Stub routers to work, otherwise....I think it gets tricky with respect to updating routes as well as getting the static routes correct.

http://www.netcordia.com/resources/books/chap3-static-routes.asp

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Which of those routers is 172.16.20.2

by NetMan1958 In reply to They run god awful RIP on ...

Is 172.16.20.2 assigned to the 3640? The reason I ask is because the 3640 has routes to a couple of subnets with a next hop of 172.16.20.2:
R 172.16.40.0 [120/1] via 172.16.20.2, 00:00:08, Serial0/0
R 173.55.0.0/16 [120/3] via 172.16.20.2, 00:00:08, Serial0/0

While the other router who's routing table you posted has a route to 192.168.X.X with a next hop of 172.16.20.2:
R 192.168.X.X/24 [120/1] via 172.16.20.2, 00:00:03, Serial0/0

From that I gather that the 3640's serial0 address isn't 172.16.20.2 and that the other router isn't sending traffic for 192.168.X.X directly to the 3640.

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Here's the route table from the DSL router

by CG IT In reply to Which of those routers is ...

173.55.107.1 255.255.255.255 * 10 eth1
173.55.107.1 255.255.255.255 * 11 ipsec0
172.16.20.0 255.255.255.0 192.168.X.X 10 eth0
192.168.X.0 255.255.255.0 * 0 eth0
172.16.30.0 255.255.255.0 192.168.X.X 10 eth0
173.55.107.0 255.255.255.0 * 0 eth1
173.55.107.0 255.255.255.0 * 0 ipsec0
172.16.40.0 255.255.255.0 192.168.X.X 10 eth0
default 0.0.0.0 173.55.107.1 40 eth0

So it looks like they have all the frame-relay networks using the 192.168.X.X as the default gateway...

well it does give the path out... I asked em to try and ping their ISP name servers and they get destination unreachable from the 172.16.20.2 interface....

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I think the 172.16.20.2 is a frame-relay interface 3640 not sure

by CG IT In reply to Which of those routers is ...

well its on another router at another site I'm told...

While they didn't give me the route table for that router I'll bet it's not right...

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A Test

by NetMan1958 In reply to I think the 172.16.20.2 i ...

Can you get a static route configured on one of the hub routers like :
ip route 0.0.0.0 0.0.0.0 X.X.X.X
where X.X.X.X is the serial0 IP of the 3640.

then try to ping the dsl router from that hub router. If it doesn't ping, try a traceroute from the hub to a IP on the Internet and see where it starts timing out.

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Here's the route table off their other router

by CG IT In reply to Which of those routers is ...

This is the 172.16.20.2 network and it's here thats the problem...


Gateway of last resort is not set

172.16.0.0/24 is subnetted, 3 subnets
C 172.16.40.0 is directly connected, FastEthernet0/0
R 172.16.30.0 [120/1] via 172.16.20.1, 00:00:15, Serial0/1
C 172.16.20.0 is directly connected, Serial0/1
R 173.55.0.0/16 [120/2] via 172.16.20.3, 00:00:07, Serial0/1
R 192.168.X.X/24 [120/1] via 172.16.20.3, 00:00:07, Serial0/1
Router#

the S0/1 interface address is the 172.16.20.2 address.

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