I have two locations, A and B which are connected via point to point switched Ethernet (flat layer 2 handoff). Location A is our main location that houses DNS, DHCP, Active Directory, Exchange, Network Shares, etc. Location A has it’s own firewall and T1 for Internet. Location B has no servers however it has its own T1 and firewall for Internet. Clients at location B obtain IP’s via DHCP and access all servers at location A through the point to point switched Ethernet. I’ve attached a rough drawing of my network.
Location B has a Cisco SG300 with a Cisco SG200 connected to it via a crossover cable. The point to point switched Ethernet and the firewall for the T1 at location B are connected to the SG300. VLAN10 is configured on the SG300 to allow clients at location B to obtain a 152.x IP address (instead of the 151.x used at location A) and to send traffic to location A . DHCP relay is enabled and there is a static route for internet traffic to go to the firewall at location B. The SG300 is the default gateway for all clients at location B.
I’ve been having an issue with some laptops that travel between location A and B not being able to connect at location B. It seems like after they return from location A to B that they are able to obtain an IP through DHCP (I can see the lease on the server at location A) however they are not able to connect to Exchange, Active Directory, Network shares, Internet, etc at location A. Running an ipconfig on the laptops give an unable to reach DNS error. From the laptops that won’t connect I’m unable to ping the SG300 or any servers at location B. I am able to ping other clients connected to the network at location B.
Initially rebooting the SG300 at location B was the only way to allow the laptops to connect however the next day there would be other laptops, or the same ones, that were unable to connect. I noticed that the following error in the Flash Memory log of the SG300 throughout the day: %ARP-E-ARPTBL: ARP Table Overflow This prompted me to lower the ARP Entry Age Out from the default of 60000 seconds to 300 seconds. Since I’ve done that it’ s been a week and there have been no laptop connection issues however I continue to receive the same error: %ARP-E-ARPTBL: ARP Table Overflow throughout the day. I fear that I will experience the same issues in the future if I cannot identify why I am receiving the ARP errors. Any suggestions. My config or the SG300 attached Thanks in advance!!!
