Solved: How does a clear ip arp x.x.x.x resolve the ping issue?

ohforce55 · ‎09-13-2018

Hi,

I recently upgraded the firewall hardware that was connected to a switch.

After upgrading the firewall (IPs are the same), I couldn't ping from the inside interface on the firewall to the switch.

I couldn't also ping from the switch to the inside interface firewall.

After I did a clear ip arp (the inside interface address of the firewall) on the switch, the ping workd.

Can anyone please how it turned to work?

Thanks in advance!

Alex Pfeil · ‎09-13-2018

Many devices will not automatically update the MAC address for an ARP entry if it is already in the table. You will have to wait for an ARP entry to time-out. Many devices have a 300 second time-out (5 minutes). An easy way to get a new device working if you cannot ping it right away is to clear the ARP table. This is usually a problem with ISP devices that can be resolved by rebooting the device or waiting patiently. So, you actually came up with the solution on your own, great job!

Please rate helpful posts.

View solution in original post

Alex Pfeil · ‎09-13-2018

Many devices will not automatically update the MAC address for an ARP entry if it is already in the table. You will have to wait for an ARP entry to time-out. Many devices have a 300 second time-out (5 minutes). An easy way to get a new device working if you cannot ping it right away is to clear the ARP table. This is usually a problem with ISP devices that can be resolved by rebooting the device or waiting patiently. So, you actually came up with the solution on your own, great job!

Please rate helpful posts.