Re: Pinging a remote router from 1900 switch

vineetaggar · ‎05-02-2003

While paractising the LAB consisting of four routers and 1900 switches, I cannot ping any remote router from the switch. I can only ping directly connected router with the LAN through ethernet interface. Can that remote router not be pinged from the switch or if it can be done how ?

Looking for a detailed reply with solution.

Thanks

Vineet Aggarwal

mark-obrien · ‎05-03-2003

Vineet,

This should work, provided that the 1900 has the proper subnet mask configured and a default gateway. This is done from the IP Configuration Menu. If your switch has Enterprise Edition software, enter the following commands in the global congiguration mode:

ip address (address) (mask)

ip default-gateway (address)

Mark

vineetaggar · ‎05-03-2003

Hi Mark,

Thanks for your response. I have already correct ip address and default gateway as of my knowledge. Default gateway of the switch is ip address of the routers ethernet interface on which it is connected locally. But, 1900 is pinging only that local router and not the romote router. Configuraton details are as follows :

1900Switch :

ip address : 172.16.10.50

Mask : 255.255.255.0

default gateway : 172.16.10.3

2514Router :

fast ethernet1(on which switch is locally connected) : 172.16.10.3

mask 255.255.255.0

fast ethernet0(on which 2501router is connected) : 172.16.10.1

mask : 255.255.255.0

2501Router:

fast ethernet0(on which 2514router is connected) : 172.16.10.2

mask : 255.255.255.0

serial0 : 172.16.20.1

mask : 255.255.255.0

And, I am not able to ping 172.16.10.2 and 172.16.20.1 from 1900switch.

But, I can ping from 2514router. This shows there is no connectivity problem between the routers. I am running static routing. Kindly guide me if something wrong has been configured or if there is need of some other configuration.

Vineet

mark-obrien · ‎05-04-2003

Vineet,

Thank you for the description.

When the switch tries pinging 172.16.10.1 and 172.16.10.2, it considers these addresses as being local, since they are on the same subnet as itself. Therefore, it will not send packets for these addresses to the default gateway. It will instead send ARPs out to resolve the IP addresses to MAC addresses, but the routers having these addresses will not respond because they are not physically on the segment.

You must set up the segment between the 2514 router and the 2501 router with a different subnet that the segment that the 1900 sits on. These segments do not connect to each other physically, and they should not be addressed as though they were.

Good luck.

Mark

vineetaggar · ‎05-05-2003

Mark,

2514 router and 2501 router are connected through ethernet physically. But, I could not understand the statements in the last para. Can you please be specific about what exactly shall I do. Or can you send me a link which describes such a situation so that I can refer to it.

Thanks

Vineet

mark-obrien · ‎05-06-2003

Vineet,

Your description indicates that the 2514 has the address 172.16.10.3/24 on one ethernet interface that connects to the 1900 switch, and the address 172.16.10.1/24 on another that is connected to the 2501. Do I understand your description correctly? My point was that these two interfaces are considered to be two different segments, and as such should have different subnet addresses assigned to them. As it is, you have the subnet 172.16.10.0/24 assigned to two different interfaces of the 2514.

I can not give advice on what you should do, since I don't know what you are trying to accomplish. Are you trying to put several routers on the same LAN? If so, connect them all to the 1900 switch and assign addresses to them in the 172.16.10.0/24 subnet. Are you trying to set up routers on several different LANs and WANs? If so, keep your existing physical connections and assign different subnets to each segment.

Good Luck.

Mark

vineetaggar · ‎05-07-2003

Mark,

I tried it the way you told me but when I design it including the switches it doesn't work.

Vineet

mark-obrien · ‎05-08-2003

Vineet,

Do the routers that are not connected to the 1900 have routes to the 1900's subnet? They will need routes back to that subnet if a ping is to be successful.

Mark

vineetaggar · ‎05-10-2003

Mark,

I am running static routing and every router is having entries in its routing table for every subnet. and everything except switch is pinging each other.

Vineet

mark-obrien · ‎05-11-2003

Can you send your configs?

vineetaggar · ‎05-11-2003

Ya sure,

This time I have build a very simple network with one 2621 router, two 1900 switches, and four PCs whose configurations are as follows:

I have used 2621 router's fastethernet port for different networks:

interface eth0's config is :

ip : 172.16.1.1

mask : 255.255.255.0

interface eth1's config is :

ip : 172.16.2.1

mask : 255.255.255.0

one 1900 switch fastethernet post is connected to the router's fastethernet port(let's say:subnet 1)

swicth ip is : 172.16.1.2

mask: 255.255.255.0

two PCs are connected to that switch having the IPs of same subnet.

second 1900 switch is connected to the other interface of the router on the other subnet(subnet 2)

switch's ip is : 172.16.2.2

mask: 255.255.255.0

and two other PC's are connected to this one on this subnet.

Now the problem is switch which is on subnet 1 is not able to ping the devices on the subnet 2 including the interface having ip 172.16.2.1 and vice-versa.

And let me tell you one thing I am using the boson simulator software for practise not the actual devices if this information could be of use for u.

thnx for ur interest.

Vineet

mark-obrien · ‎05-13-2003

Earlier, you said that the default gateway of the 1900 is 172.16.10.3. Have you changed that to reflect the new subnet? Please show me the default gateway.

vineetaggar · ‎05-13-2003

Yes Mr. Mark,

This time I build a very different design. I thought why not try it with a very simple network with one 2621 router, two 1900 switches, and four PCs whose configurations are as follows:

I have used 2621 router's fastethernet port for different networks:

interface eth0's config is :

ip : 172.16.1.1

mask : 255.255.255.0

interface eth1's config is :

ip : 172.16.2.1

mask : 255.255.255.0

one 1900 switch fastethernet post is connected to the router's fastethernet port(let's say:subnet 1)

swicth ip is : 172.16.1.2

mask: 255.255.255.0

def-gateway : 192.168.1.1

two PCs are connected to that switch having the IPs of same subnet.

second 1900 switch is connected to the other interface of the router on the other subnet(subnet 2)

switch's ip is : 172.16.2.2

mask: 255.255.255.0

def-gateway : 192.168.2.1

and two other PC's are connected to this one on this subnet.

Now the problem is switch which is on subnet 1 is not able to ping the devices on the subnet 2 including the interface having ip 172.16.2.1 and vice-versa.

And let me tell you one thing I am using the boson simulator software for practise not the actual devices if this information could be of use for u.

thnx for ur interest.

Vineet

mark-obrien · ‎05-13-2003

Make the default gateway for switch 1 172.16.1.1, and the default gateway for switch 2 172.16.2.1. Right now, you show them as 192.168.1.1 and 192.168.2.1, respectively.

Mark

vineetaggar · ‎05-14-2003

Mark,

I have tried it as you say. Should it work properly if so configured ?