VLAN problem with ROAS

[ARPhillips]

Hi all,

I'm currently studying for my CCNA and have set up a home lab up till now been using packet tracer. On the sim I have no problem as all setting up a ROAS. Translate it to real life and I can't get it to work. I have a real basic running-config on both switch and router. Nothing can ping anything. 

I've followed CBTnuggets videos and checked my configs against the ones in the lab to no avail. On a debug the only thing I saw out the ordinary was the trunk port going down and then back up every time the PC was trying to ping. 

I've attached both running configs, any help would be much appreciated. 

PS: I did disable the windows firewall as well, just in case

[Richard Burts]

Ross

The first part of the debug output that you posted makes sense (sort of). You issued the ping command and the router sends arp requests trying to resolve what mac address is used for the destination address. There was no response and the ping failed.

The other debug output is puzzling

IP ARP rep filtered src 10.1.50.1 000b.5faa.51c0, dst 10.1.50.1 ffff.ffff.ffff it's our address

This is an arp request where the source IP and the destination IP are the same. This is a common way for a host to check to be sure that there is not another device using the IP that this host wants to use. But who is issuing that request? I am under the impression that you changed the router config so the router should no longer be checking for 10.1.50.1. So who is doing this?

I am wondering about the arp output that you posted from the switch. You have one switch port assigned to vlan 50. But it is reporting 2 IP addresses. How do we have 2 IP addresses on that one interface? Can you post a fresh copy of the show arp from the switch?

HTH

Rick

[ARPhillips]

So I've come back to the router and the IP ARP message now has the correct address (10.1.1.1 not 10.1.50.1)

The SW1 current show arp command gives this.

SW1#show arp
Protocol  Address          Age (min)  Hardware Addr   Type   Interface

Internet  10.1.1.50               0   b4b5.2f2c.e9ab  ARPA   Vlan50
Internet  10.1.1.100              -   000d.296a.e580  ARPA   Vlan50
Internet  10.1.1.200              0   c860.00a2.f262  ARPA   Vlan50

Kind regards,
Ross

[ARPhillips]

This is interesting (or may not be … ) but with sh ip route in real life I get 

     10.0.0.0/24 is subnetted, 1 subnets
C       10.1.1.0 is directly connected, FastEthernet0/0.50

on the sim (picking out one of three subinterfaces) I have 

      172.16.0.0/16 is variably subnetted, 8 subnets, 2 masks

C       172.16.0.0/20 is directly connected, GigabitEthernet0/1.10

L        172.16.10.1/32 is directly connected, GigabitEthernet0/1.10

I'm aware different ips and masks but the real life router hasn't got its local IP address on the interface. At least that's what it looks like to me. 

Ignore that, I've just seen its only in IOS 15

[Richard Burts]

Ross

Would you post the output of show cdp neighbor from both the router and the switch?

Would you enable debug arp and then try to ping the switch address?

HTH

Rick

[ARPhillips]

Hi Rick,

R1#sho cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
                  S - Switch, H - Host, I - IGMP, r - Repeater

Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID
R1#debug arp
ARP packet debugging is on

R1#ping 10.1.1.100

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.1.100, timeout is 2 seconds:

*Mar  1 00:08:10.647: IP ARP: creating incomplete entry for IP address: 10.1.1.100 interface FastEthernet0/0.50
*Mar  1 00:08:10.647: IP ARP: sent req src 10.1.1.1 000b.5faa.51c0,
                 dst 10.1.1.100 0000.0000.0000 FastEthernet0/0.50.
*Mar  1 00:08:12.647: IP ARP: sent req src 10.1.1.1 000b.5faa.51c0,
                 dst 10.1.1.100 0000.0000.0000 FastEthernet0/0.50.
*Mar  1 00:08:14.647: IP ARP: sent req src 10.1.1.1 000b.5faa.51c0,
                 dst 10.1.1.100 0000.0000.0000 FastEthernet0/0.50.
*Mar  1 00:08:16.647: IP ARP: sent req src 10.1.1.1 000b.5faa.51c0,
                 dst 10.1.1.100 0000.0000.0000 FastEthernet0/0.50.
*Mar  1 00:08:18.647: IP ARP: sent req src 10.1.1.1 000b.5faa.51c0,
                 dst 10.1.1.100 0000.0000.0000 FastEthernet0/0.50.
Success rate is 0 percent (0/5)

The show cdp neighbors is the same on the switch and router. Both empty. 

[ARPhillips]

Hi Georg, 

Thanks for replying, I don't have the no ip routing command on thee switch. It's a layer 2 device so I thought IP routing would be beyond it. If I set DHCP then I get no addresses, I can't send PINGS across to the router and the router cant seem to ping out either. 

I am aware its old but it is for a small home lab and using Packet Tracer with exactly the same hardware and IOS versions I can make this work with 2+ VLANS in moments. For some reason its just not translating to real world. 

Kind regards,

Ross

[Richard Burts]

Ross

Thanks for the information. I believe that we are making progress. Both the fact that the arp request from router to switch fails, and the fact that cdp is not seeing neighbors both point to the fact that the router and the switch are not communicating at a basic level. It is not a problem with addressing or with routing or anything like that. They are basically not communicating. 
Can you post the output of these commands: on the router show ip interface brief and on the switch show interface status.

I can think of two things to investigate.

1) is it possible that there is a problem with the cable connecting the router and switch?

2) is it possible that there is a problem with 802.1q encapsulation. Both devices seem to support it but is it possibly not working?

To address these:

1) do you have another cable that you can try? And for router to switch it should be a normal straight through cable and not a cross over.

2) can we eliminate the trunking? Would you configure the switch interface as an access port in vlan 50 instead of as a trunk? And would you remove the sub interface configuration on the router (or at least remove the IP address from it) and configure the router interface as a normal physical interface and configure the IP address on the physical interface?

HTH

Rick