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ARP is in Complete -- Urgent help req - Problem is going on

Dipesh Patel
Level 2
Level 2

Dear all,

We have facing a strange problem.

ARP is incomplete for some of the hosts in Cisco 3560 switch. We have replaced the switch with cisco 3750 but the problem remian as it is.

Can you tell why this ?

It;s urgent the issie is going on right now.

Regards,

6 Replies 6

cadet alain
VIP Alumni
VIP Alumni

Are all the hosts in the same VLAN? what if you put one of these host in a port where other host is working?

Did you try reloading?Are there any logs? Are these hosts directly connected ?

can you post your running config.

Regards.

Alain.

Don't forget to rate helpful posts.

Dear Expert,

All the hosts are in diff Vlans.  All Vlans on Dist l3 switch . From Dist L3 switch all the access switch are connected.

Hosts are connected to Access switches.

Pls reply

samavedula_rama
Level 1
Level 1

1) Please check if there is appropriate route to the host which shows incomplete

2) Make sure you have Proxy Arp enabled on the connected switch interfaces if you have Static routes configured towards them.

3) Make sure you are learning the mac-addresses on the interfaces you connect hosts on and you've configured them with the correct IP addresses and masks.

Would've been good if you posted the topology and told us where you are seeing the problem.

Dear All,

Topology like this

CORE --- to --- Distribution (L3) --- to --- Access

in Distribtuion 9 Vlans are there.

In all vlans some of the iPs are communicated but some of are not and if I show in sh arp i fond that incomlete arp .

this ditribution has default route to CORE switfch and core switch has reverse route to Distribution for all the Vlans in Dist. Switch.

All Vlans in Dist has proxy arp is disable.

Regs

Okay so here is the scenario.

How is the static route setup ? Are you pointing at the interface or next-hop?

I ask this becuase, if you have a default route pointing out an interface, arp will be done for destination address. And if you have Proxy-Arp disabled on the next hop, that ARP will never be complete if you are pinging to an IP address from a different network.

If static default routes are pointing out the next-hop, then ARP will be done for the next-hop and the packets are forwarded there regardless if that interface has proxy-arp enabled or disabled.

So, if you have such kind of setup, try using the static routes pointing out the next-hop instead of the interface or try using the combination of both or enable Proxy ARP on VLAN interfaces.

Thanks.

Dear,

Can I call you if possible ? Contact no pls.

Topology config is like :

On CORE switch e.g.:

VLan 100 : ip add 10.10.100.1 255.255.255.0

ip route 10.10.1.0 255.255.255.0 10.10.100.11

ip route 10.10.2.0 255.255.255.0 10.10.100.11

ip route 10.10.3.0 255.255.255.0 10.10.100.11

Distribtuion:

vlan 1 : ip add 10.10.1.1 255.255.255.0  --  ip Proxy arp disable

vlan 2 : ip add 10.10.2.1 255.255.255.0 -- Proxy arp disable

vlan 3 : ip add 10.10.3.1 255.255.255.0 -- Proxy arp disable

ip route 0.0.0.0 0.0.0.0 10.10.100.1

Access switch :

Default geteway to Dist switch

Host are connected here.

Also tried after enabling Proxy arp

Regards,

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