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Mia_27938's avatar
Mia_27938
Icon for Nimbostratus rankNimbostratus
Oct 25, 2012

The qustion about the ARP broadcast on the BIG-IP

Hi,

 

I have the qustion about the ARP broadcast on the BIG-IP

 

I know that the default behavior about ARP option on the BIG-IP is,

 

- Dynamic Timeout 300seconds

 

- Request Retries 6 times

 

- Request interval is 2 seconds

 

I refered to the following article.

 

Manual Chapter: Configuring Address Resolution Protocol

 

BIG-IP system repeatedly broadcasts the ARP request until a host sends a response, or until the maximum number of allowed requests is reached. (The maximum number of requests to the same host that the BIG-IP system can make is a setting that you configure.) If the system sends the maximum number of ARP requests and does not receive a response, the host is declared to be unreachable, and the system sets the state of the entry toDOWN. For more information on the DOWN state, see Understanding ARP entry states on this page.

 

 

Recently, I captured the ARP request packets, sended by the BIG-IP, on the HP 12500 switch.

 

 

BIG-IP ============= HP 12500 switch ============Web servers

 

10.10.2.134 10.10.2.134

 

 

I attached the realted text file. please refer to it.

 

Look at the attached text file, it can be seen that the arp reqeusts packets was sent not at 2-second intervals.

 

Even twice per a second..

 

I seems that the arp broadcast packets be sending too frequently.

 

Why is this?

 

 

Thak you

 

Chaibin.

 

 

 

 

 

 

management
monitoring

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  • What_Lies_Bene1's avatar
    What_Lies_Bene1
    Icon for Cirrostratus rankCirrostratus
    Oct 25, 2012
    If you did the capture on the switch by capturing the VLAN rather than just the port connecting the F5 then you might be seeing the same ARP packet multiple times as it's forwarded to each relevant port in that VLAN. I'd suggest you fine tune your capture somewhat by restricting the capture to the ingress port or making it more verbose so it displays the VLAN and port the packet is seen on.
  • nitass's avatar
    nitass
    Icon for Employee rankEmployee
    Oct 25, 2012
    how did you test?

    i created a fake pool and tried to access virtual server (http://172.28.19.79). 

    [root@ve10:Active] config  b virtual bar list
virtual bar {
   snat automap
   pool foo
   destination 172.28.19.79:80
   ip protocol 6
}
[root@ve10:Active] config  b pool foo list
pool foo {
   members 200.200.200.102:80 {}
}

[root@ve10:Active] config  tcpdump -nni internal arp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on internal, link-type EN10MB (Ethernet), capture size 108 bytes
20:23:17.769685 arp who-has 200.200.200.102 tell 200.200.200.10
20:23:20.770108 arp who-has 200.200.200.102 tell 200.200.200.10
20:23:23.750956 arp who-has 200.200.200.102 tell 200.200.200.10
20:23:26.310630 arp who-has 200.200.200.102 tell 200.200.200.10
20:23:28.871639 arp who-has 200.200.200.102 tell 200.200.200.10
20:23:31.432153 arp who-has 200.200.200.102 tell 200.200.200.10
20:23:33.992251 arp who-has 200.200.200.102 tell 200.200.200.10