ARP issue on layer 2 cisco switch

[vishwanath1983]

We are facing strange Arp Broadcast issue on Cisco switch 350

We have ISP link terminate on cisco router C841M

ISP has provide 2 pool with different Ip address.

Configuration on router,

WAN interface has been configured with 2 IP address primary and secondary ip address on single interface of router.

from there link is terminated on F5 device .

in this scenario everything is working fine .

But if i connected same link from ROUTER to cisco layer 2 switch model 350 and from same switch to F5 device.

my primary ip address pool on router goes unreachable

logs on F5

2 0.353116 0.000000 Cisco_f9:e6:33 → Broadcast ARP IN s1/tmm0 :
7 1.589101 1.235985 Cisco_f9:e6:33 → Broadcast ARP IN s1/tmm0 :
12 2.490582 0.901481 Cisco_f9:e6:33 → Broadcast ARP IN s1/tmm0 :
19 2.829271 0.338689 Cisco_f9:e6:33 → Broadcast ARP IN s1/tmm0 :
29 4.211825 1.382554 Cisco_f9:e6:33 → Broadcast ARP IN s1/tmm0 :
30 4.291621 0.079796 Cisco_f9:e6:33 → Broadcast ARP IN s1/tmm0 :
31 4.778336 0.486715 Cisco_f9:e6:33 → Broadcast ARP IN s1/tmm0 :

getting ARP log on F5 of cisco switch which is broadcasting arp

[Flavio Miranda]

@vishwanath1983 

Cisco CBS350 is not exactly a layer2 switch. It is more like a layer3 switch. But, I dont believe you can have the same setup as you do with the router.

Why dont you create two interfaces vlan and connect your ISP in one vlan and the F5 in another interface vlan and enable "IP routing" on the switch?

[vishwanath1983]

Yes we tried doing 2 vlan interface on Router for 2subnet of same  ISP WAN pool and trunk port connect to Same cisco switch and from switch to F5.

but still we are getting ARP issue and my primary ISP pool goes down.

So we are planing to deploy Layer 3 switch in place of router which will be connected to switch with trunk link and switch to F5 with trunk .

i am suspecting  mentioned switch maybe creating problem.Any idea to troubleshoot arp issue cause

[Flavio Miranda]

 Not easy to help as we dont know pretty much the copology. Is your F5 standalone or cluster?

If you create a vlan dedicate to the ISP, add to it IP address, why are you ISP going down? And what do you call ISP pool?

The ARP can be only a reaction of link flapping.

Can you draw a simple topology ?

[vishwanath1983]

On router same ISP  has two different Ip address pool configure under single interface has primary and secondary ip address .

On switch we have created vlan for link coming form router and same vlan output to F5 HA device . in this scenario  intermediate isp primary ip address pool goes down , and we receive arp broadcast on F5 from layer switch .

2 0.353116 0.000000 Cisco_f9:e6:33 → Broadcast ARP IN s1/tmm0 :
7 1.589101 1.235985 Cisco_f9:e6:33 → Broadcast ARP IN s1/tmm0 :
12 2.490582 0.901481 Cisco_f9:e6:33 → Broadcast ARP IN s1/tmm0 :
19 2.829271 0.338689 Cisco_f9:e6:33 → Broadcast ARP IN s1/tmm0 :
29 4.211825 1.382554 Cisco_f9:e6:33 → Broadcast ARP IN s1/tmm0 :
30 4.291621 0.079796 Cisco_f9:e6:33 → Broadcast ARP IN s1/tmm0 :
31 4.778336 0.486715 Cisco_f9:e6:33 → Broadcast ARP IN s1/tmm0

[paul driver]

Hello
Do you have any static route pointing to a nexthop physical interface of the wan /F5 interface 

[vishwanath1983]

yes we have static route pointing to a nexthop physical interface of the wan /F5 interface .