I help manage a WISP network which has a Cisco 3750 at its core and a couple of Cisco 7200 routers to two separate ISPs. We have configured public and private VLANs. The infrastructure is based on point to multipoint links with cisco SG300 switches at each main location. I have a problem where devices are not contactable until the ARP cache on the router is cleared or they are pinged from a device on the local LAN. It seems that as soon as the switch times out the address from the CAM tables, it will not respond until the ARP cache is cleared. A simple example is this.
All devices remain active up to the AP. The CP and customer will drop off the network randomly. I would expect the traffic to refresh the CAM table as per normal. The ARP cache on the router shows the exact same information before and after clearing so there is no spoofing or eroneous info there. This is not an isolated case, it is exactly the same across all of the other devices in the setup.
This has only become apparant since moving the devices to being managed in VLAN 201. prior to that, the client had everything (over 3000) devices in VLAN 1 with public IPs along side Private. Obviously a problem.
Anyone seen this sort of problem and able to offer any tips, ideas or suggestions? I am all out of ideas.
Just to add to this. I have read a lot of information about HSRP and having to synce CAM and ARP tables. I am not using HSRP and in this case, the second 7200 router is connected to a different ISP and operates completely separately.
In light of the information on HSRP. I have reduced the ARP timer for the two VLANs to 240 seconds, which being less than the CAM timer of 300 seconds means that the CAM table always remains up to date. I see this as a work around because it will obviously lead to a large amount of ARP traffic but it does seem to fix this problem. I am not sure why when the CAM table loses the MAC address, fresh traffic doesn't reach the switch and trigger the update of the CAM table. It seems like the traffic is not being sent to the right place.
Cisco Digital Network Architecture Center Tools <Template Editor > In this article, we are going to talk about the Cisco Digital Network Architecture Center Template Editor tool.Cisco DNA Center gives us the flexibility and scalability to confi...
Community Live- Cisco SD-WAN Policies: Leveraging the Full Power of Cisco SD-WAN
(Live event - formerly known as Webcast- Tuesday 24 March, 2020 at 10 am Pacific/ 1 pm Eastern / 6 pm Paris)
This event had place on Tuesday 24th, March 2020 at 10hrs P...
IS there a way to upgrade the ios on a cisco 9200l switch using a usb drive instead of using a tftp server? If so could someone point me to the article or tell me how this can be done? These switches seem to be more complicated than previous switches. Tha...
Hello,I'm needing to integrate the Cisco Firepower 2110 into our Data Center JUST to fulfill Site-to-Site and Remote Access VPN. My SD-WAN ISRs already have FW and IPS running, which is what I want since I have internet breakouts at my branches, so this D...
Hi, Switch 1 and switch 2 connected via trunk. Both configured with new vlan 3.When creating new vlan 3, is it need to include "Spanning-tree vlan 3 priority 8192"- Sw 1 and "Spanning-tree vlan 3 priority 16384"-Sw 2?What will happen for those s...