arp issue - one for the networking guys....

[stek]

Having trouble connecting to some of our hosts, strange thing happening;

1. When I ping, ssh, scp to some of our hosts, it times out/broken pipe. Reason is the hosts ip in my arp table seem to have acquired the gateway's mac address and confuses it.

2. When I scan the network with a scan tool, seems every unused ip in our subnet is now listed and has the gateway's ip.

3. The gateway is actually a Cisco ASA 5505 that gives out DHCP etc but these are statics outside the DHCP range.

4. The only other networking kit is a CISCO 2960 and Netgear GS724.

5. I'm using OS X which I believe has arp issues....

6. Some of the cables are very poor - crimped - could this be an issue?

I can override by manipulating the arp table but that's a PITA, something is fundamentally wrong.

Any ideas?

[Scruff]

Erm...

Flush the ARP table?

[DimPrawn]

Erm...

Flush the ARP table?

[stek]

Erm...

Flush the ARP table?

Done that, try to reconnect to affected hosts, arp table shows IP has having the gateway's mac address again. Only workaround I have is;

arp -d -a

arp -s ip mac (for effected hosts)

[Acme Thunderer]

I ain't a network bod and I could be teaching grandma to suck eggs here, but you are sure the host thinks its on the right subnet or you haven't got a routing table glitch?

If everything is showing the gateway mac address for its IP, it could be that the host is trying to route everything. This would explain why the Gateway MAC address is listed for all the IP addresses.

[stek]

I ain't a network bod and I could be teaching grandma to suck eggs here, but you are sure the host thinks its on the right subnet or you haven't got a routing table glitch?

If everything is showing the gateway mac address for its IP, it could be that the host is trying to route everything. This would explain why the Gateway MAC address is listed for all the IP addresses.

Cheers for replying...

Network is dead simple, hosts ---> switch ---> Firewall/VPN ----> internet.

All routing is done on the ASA, nothing other than basic on the hosts, dead straightforward, default route is the ASA, really simple.

At first I thought it's just an issue with my Mac, but it isn't, some of the new hosts are showing the same too, I think it's arp on the ASA, and it's too hard for me!

[Normie]

Cheers for replying...

Network is dead simple, hosts ---> switch ---> Firewall/VPN ----> internet.

All routing is done on the ASA, nothing other than basic on the hosts, dead straightforward, default route is the ASA, really simple.

At first I thought it's just an issue with my Mac, but it isn't, some of the new hosts are showing the same too, I think it's arp on the ASA, and it's too hard for me!

Is your scenario similar to https://supportforums.cisco.com/disc...ot-same-subnet


The solution there was to set up a static arp entry on the ASA and internet router/gateway/modem

[stek]

Is your scenario similar to https://supportforums.cisco.com/disc...ot-same-subnet


The solution there was to set up a static arp entry on the ASA and internet router/gateway/modem

Cheers...

Not the same though, internally we are all 10.22.22.0/24 and ASA and default route/gateway is 10.22.22.1