Why would arp not send over trunk

[Zakarakus]

When I ping a remote address from Subnet A, ARP behaves as it should and broadcasts across the switched network until it hits the device with the address, etc. But if I ping the same remote IP from Subnet B, the ARP packet is sent to the access switch and then drops. No errors - packet inspection seems to indicate the packet will be broadcast on all interfaces except the one on which is was received but this is not happening. I have copied the config from one switch to another. identical hardware and version, only changing hostname, vlan names and interfaces. Am I going mad? 

Attached the .pkt file. Please help before I rage quit my career. 

Really basic configuration here - this should be simple! Argh... 

[Martin L]

Not sure how or who pings who since I do not see Subnet A and B , but I see some errors on main L3 switch.

In order for any hosts be able to communicate, we must have trunks up and allowing vlans, SVI in up up state, ip routing enabled is you ping remote subnets. This means we need: enable trunking, match vlans on switches, match if enabled VTP settings to propagate vlans across domain or leave VTP to default and add vlan manually; 

RAG_CORE_4500#

RAG_CORE_4500#18:03:00 %DTP-5-DOMAINMISMATCH: Unable to perform trunk negotiation on port Fa0/2 because of VTP domain mismatch.

18:03:30 %DTP-5-DOMAINMISMATCH: Unable to perform trunk negotiation on port Fa0/2 because of VTP domain mismatch.

From above messages, it looks like L3 main switch and L2 VLAN 700 switch are misbehaving. Fix that should let you ping OK

Regards, ML
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[Zakarakus]

Thank you for your response Martin and apologies for the frustrated phrasing of my problem.

VLAN 1010 appears to be unreachable. When trying to ping either 192.168.10.251 (int vlan 1010 on RAG_CORE_4500) or 192.168.10.4 (PC2), the arp packet is not behaving as expected. I imagine I have overlooked something in the config and it is my own error. 

The real thing that is puzzling* me though is that when sending a ping from 192.168.10.4 (PC2), the arp packet is sent to the VLAN1010 2960 switch but the broadcast is then only sent out on access port-fa0/2 and not the trunk_link-fa0/1. This is not how I thought that arp behaved when broadcast. 

Thank you again for you time and patience. 

(*driving me crazy)

[Georg Pauwen · Accepted solution]

Hello,

the problem is that extended Vlans are not supported in Packet Tracer. You can verify this by trying to add Vlan 1010 to the allowed list on a trunk, you will get the error below:

RAG_CORE_4500(config-if)#switchport trunk allowed vlan 1010
Command rejected: Bad VLAN list

So you are not doing anything wrong, to the contrary. It is just one of the (many) limitations of the software...

[Georg Pauwen · Accepted solution]

Hello,

except for the fact that there was a VTP mismatch on all switches, the top PC was assigned to the wrong Vlan (1 instead of 1001).

The problem with the lower switch (VLAN1010) was that Packet Tracer does not seem to support extended Vlans (higher than 1005).

I changed Vlan 1010 to Vlan 101, and everything can now ping each other.

Attached the working file (saved in PT version 8).

[Zakarakus]

Thanks so much for taking the time to explain, Georg. I am glad it was a software restriction and not my entire understanding of Cisco S and R failing me on the most basic of concepts. That is annoying - I would use GNS3 but there is a bug in the current version so can't create a test env with that either.

Maybe I will alter the VLANS and make sure I identify them - perhaps put the real VLAN as the name...Thank you again!