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Community Member

ARP table Question

On a MSFC how can I tell what my ARP Agingtime is? Also, would a router at anytime just update it ARP table? Here is a small sample from my ARP table it seems like the router isn't holding the enties all long as it should. Any Ideas??? These machines are on all day long I shouldn't the entry be held for a longer period of time?

Internet 172.xx.31.161 1 00b0.d041.bb9b ARPA Vlan31

Internet 172.xx.21.171 3 00b0.d085.ca5c ARPA Vlan21

Internet 172.xx.24.166 3 0006.5b2b.1990 ARPA Vlan24

Internet 172.xx.33.159 5 00b0.d040.5e25 ARPA Vlan33

Internet 172.xx.22.168 5 0000.864b.850e ARPA Vlan22

Internet 172.x.54.136 6 00b0.d041.563d ARPA Vlan54

Internet 172.xx.70.248 58 0001.e62d.2329 ARPA Vlan70

Internet 172.xx.52.141 0 00b0.d072.3ef0 ARPA Vlan52

Internet 172.xx.54.143 0 0006.5b6e.5dfb ARPA Vlan54

Internet 172.xx.24.161 1 00b0.d083.6480 ARPA Vlan24

Internet 172.xx.33.152 2 00b0.d052.6a17 ARPA Vlan33

Internet 172.xx.21.172 3 0006.5b6c.90d1 ARPA Vlan21

Internet 172.xx.53.140 3 00b0.d047.a8ec ARPA Vlan53

Internet 172.xx.63.134 3 0004.7571.8351 ARPA Vlan63

Internet 172.xx.62.135 7 00b0.d098.29ed ARPA Vlan62

Internet 172.xx.31.166 8 0003.470f.27da ARPA Vlan31

Internet 172.xx.60.133 8 00b0.d052.0918 ARPA Vlan60

Internet 172.xx.34.155 9 0006.5b6c.90c7 ARPA Vlan34

Internet 172.xx.32.153 9 00b0.d071.1341 ARPA Vlan32

Internet 172.xx.40.144 0 0010.a48b.8475 ARPA Vlan40

Internet 172.xx.54.142 1 00b0.d04c.a86c ARPA Vlan54

Cisco Employee

Re: ARP table Question

The default aging-time for ARP entries is 4 hours. All entries remain for four hours unless there is a STP TCN. Check for STP TCNs on the associated VLANs. In addition, before an ARP ages out, it sends an ARP request for the some-to-be aged host.

Community Member

Re: ARP table Question


The default ARP timeout is four hours. But you can change it according to ur req.

command to change the arp aging time is

router(config)#int ethernet 2/0/0

router(config-if)#arp ?

arpa Standard arp protocol

frame-relay Enable ARP for a frame relay interface

probe HP style arp protocol

snap IEEE 802.3 style arp

timeout Set ARP cache timeout

router(config-if)#arp time

router(config-if)#arp timeout ?

<0-4294967> Seconds

Incase of switch follow the below one.

switch(console)> set arp agingtime

agingtime : Keyword that specifies the period of time after which an ARP entry is removed from the ARP table. agingtime Variable that specifies the number of seconds (from 0 to 1000000) for which entries will remain in the ARP table before being deleted. Setting this value to 0 disables aging.

you can configure a static or permanent ARP entry that maps the IP addresses of those devices to their MAC addresses. You can configure an ARP entry so that it does not age out, by configuring it as either static or permanent. When you configure a static ARP entry using the set arp static command, the entry is removed from the ARP cache after a system reset. When you configure a permanent ARP by using the set arp permanent command, the ARP entry is retained even after a system reset.

Command to do this : set arp [dynamic | permanent | static] {ip_addr hw_addr}

Hope it helps.


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