Proxy ARP

[m.salcedo]

Hi Expert,

Just want to ask what list of codes or IOS the proxy-arp is disable by default? And also how i can confirm that proxy-arp is disable by default?

Becasue i noticed some IOS the proxy-arp is disable by default but some are enable by default.

I tried to search it on cisco website and internet the list of IOS but no luck.

Thank in advance.

Your help is highly appreciated.

Regards,

Michael

[Alexey Stytsenko]

You can check configuration on per-port basis:

sh ip interface fa0/1 | i Proxy

or per-router basic

sh run all | i proxy-arp

Based on this command you can make conclusion is proxy-arp disabled by default or not.

[m.salcedo]

Hi Alexey,

Thanks for the response. I ran the command show ip inter | i Proxy. Some interface are disabled and some are enabled. So we could not tell which is the one is the default.

core2_ash#sho ip int | i Proxy

Proxy ARP is enabled

  Local Proxy ARP is disabled

  Proxy ARP is enabled

  Local Proxy ARP is disabled

  Proxy ARP is enabled

  Local Proxy ARP is disabled

  Proxy ARP is disabled

  Local Proxy ARP is disabled

  Proxy ARP is disabled

  Local Proxy ARP is disabled

Is there other way to check which is the default configuration aside from the two commands above?

Many Thanks.

Regards,

Michael

[Alexey Stytsenko]

In documents stays that it enabled by default on Cisco routers under Cisco IOS and Cisco IOS XE but disabled under Cisco IOS XR.

Under IOS XE there is a command to turn off proxy arp globally:

ip arp  proxy disable 

Under IOS you can use similar syntax:

no ip arp proxy 

So I suppose if it turned off globally by default you must find this command in "all" config - sh run all | i proxy

To check i can suggest you bring router to default configuration (temporary - only to make test) and run commands i adduce. If you will discover that proxy arp disabled on interfaces, im rather sure you must find no ip arp proxy in configuration file.

[m.salcedo]

I have a test switch which i a deleted all configuration (vlan.dat and config.text). It looks the command only applicable on certain IOS.

Test_Switch#sh run all

                   ^

% Invalid input detected at '^' marker.

Test_Switch#sh run all | i proxy

                   ^

% Invalid input detected at '^' marker.

Test_Switch#

Test_Switch#sh run | i proxy

Test_Switch#

On this IOS the proxy arp is enabled by default. I confirmed it since no config on this switch, only management VLAN.

Test_Switch#sh ip int | i Proxy

  Proxy ARP is enabled

  Local Proxy ARP is disabled

Test_Switch#

Test_Switch#sh ver | i Version

IOS (tm) C3550 Software (C3550-I5Q3L2-M), Version 12.1(13)EA1a, RELEASE SOFTWARE (fc1).

Do you have any cisco link that document says that it enabled by default on Cisco routers under Cisco IOS and Cisco IOS XE but disabled under Cisco IOS XR. For Cisco IOS, is this for all firmware or code?

Because i want to know what IOS that proxy-arp is disabled by default or what command to confirm it.

Many thanks for your time.

Regards,

Michael

[Alexey Stytsenko]

For XE:

http://www.cisco.com/en/US/docs/ios-xml/ios/ipaddr_arp/configuration/xe-3s/asr1000/arp-config-arp.html#GUID-42FF9655-54E7-42D3-AA22-DF0B416E7CF6

For IOS

http://www.cisco.com/en/US/docs/ios/12_2/ip/configuration/guide/1cfipadr.html#wp1001233

For XR

http://www.cisco.com/en/US/docs/routers/crs/software/crs_r4.2/addr_serv/command/reference/b_ipaddr_cr42crs_chapter_010.html#wp8980421310

Regards,

[m.salcedo]

Hi Alexey,

Thanks for the link,  link says  Cisco IOS IP Configuration Guide, Release 12.2

For IOS

http://www.cisco.com/en/US/docs/ios/12_2/ip/configuration/guide/1cfipadr.html#wp1001233

it looks this is only for the IOS  Release 12.2

is it applicable for all IOS version or Release?

Thanks,

Michael

[Alexey Stytsenko · Accepted solution]

Here is the link for 15 IOS:

http://www.cisco.com/en/US/docs/ios-xml/ios/ipaddr_arp/configuration/15-mt/arp-config-arp.html#GUID-42FF9655-54E7-42D3-AA22-DF0B416E7CF6

You can check arp configuration guide for each IOS version explicitly, but im rather sure this is true for all versions.

If my answers were helpfull, dont forget rate them.

Regards,

[m.salcedo]

Thanks for the big help Alexey, i would rather check the IOS documentation of my all devices and verify the default configuration.

Thanks again for your time on this.

Cheers!

Michael

[paul driver]

Hello

FYI -

Proxy arp IS enabled by default in IOS, this can be tunned off on a per interface basis

int xx

no ip proxy-arp

res

Paul

[Parvesh Paliwal]

Adding more to the response from Alexey, I had gone though some tutorials in early CCNA days and it says that is it turned on by default.

May be or later, cisco decided to make it IOS specific. In this case, prepare a list of the IOS you have and verify the same online.

This is what I can say on this.