[cisco-voip] setting the ARP cache timeout for phones using DHCP option

[alalli at iinet.net.au]

   Currently Being Moderated 

CONFIGURING THE ARP CACHE TIMEOUT FOR CISCO PHONES [1]

	Hi All, 

	  

	I am hoping to configure the ARP cache timeout for Cisco phones using
the dhcp option. 

	I was wondering if anyone here has done it or can verify that this
would be correct. 

	  

	Say for example I have a DHCP pool named VOICE. 

	In this network, the CUCM is located at IP address 10.2.200.110  

	  

	I did some google searching and found a Wiki site with the various
dhcp options defined in it. 

	  

	http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol [2] 

	According to the site, dhcp option 35 is used as the ARP Cache
Timeout value and it is 4 bytes long. 

	  

	Lets say that I would like to set my arp cache timeout to be 300
seconds. 

	I convert 300 to hex and get 12C. 

	Since my field will need to be four bytes long this becomes
0000.012C. 

	  

	I think that the following dhcp pool will provide 300 seconds for the
phone ARP cache timeout. 

	  

	ip dhcp pool VOICE 

	network 10.240.1.0 255.255.255.0 

	default-router 10.240.1.1 

	option 150 ip 10.2.200.110 

	option 35 hex 0000.0c12            

	  

	Can anyone help me out with a verification or point me in the
direction of the appropiate documentation? 

	  

	Many thanks for any assistance. 

	  

	Regards 

	  

	Amanda Lalli-Cafini 

Links:
------
[1] http://webmail.iinet.net.au/MESSAGE/3751318#3751318
[2] http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol

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