Re: Unable to see proxy arp working for a staic nat entry on Cisco ASA

jamesholley · ‎01-25-2022

Hi Guys

I have an HA pair of ASA5508 firewalls and I am having trouble getting a simple static Nat statement working.

I am unable to see any traffic towards the interface VIP hitting my outside interface of the firewall.

I have run a capture for arp specifically, and I don't see any requests come in from the directly connected switch to request the mac address of the IP in question.

I have a exact same set up working OK on another firewall that is a single instance (non HA) and it works fine. Replicating it on this firewall pair has seen issues.

The Nat statement itself looks fine, and packet tracer confirms that everything looks good when you simulate a packet.

IOS = Cisco Adaptive Security Appliance Software Version 9.8(4)32

Nat statement

nat (OUT_CORP,FB_LIMS) source static BM_RSD_Remote_Access_Network BM_RSD_Remote_Access_Network destination static RSD_NAS_VIP_10.x.x.167 FB_SOPHOS_RAVPN_NAT_192.x.x.2 service https https net-to-net

I assumed that proxy arp works by default when using a VIP. The VIP sits in the same /28 subnet that is configured on the outside interface.

ARP CAPTURE

hostname/act/pri(config)# sh cap arp

15 packets captured

1: 18:10:50.344296 arp who-has 10.x.x.161 tell 10.x.x.164

2: 18:10:50.345761 arp reply 10.x.x.161 is-at 0:0:c:9f:fa:8e

3: 18:10:50.345959 arp reply 10.x.x.161 is-at 0:0:c:9f:fa:8e

4: 18:16:03.062039 arp who-has 10.x.x.164 (70:b3:17:e4:70:a8) tell 10.x.x.161

5: 18:16:03.062222 arp reply 10.x.x.164 is-at 70:b3:17:e4:70:a8

6: 18:21:07.986948 arp who-has 10.x.x.164 (70:b3:17:e4:70:a8) tell 10.x.x.161

7: 18:21:07.987131 arp reply 10.x.x.164 is-at 70:b3:17:e4:70:a8

8: 18:26:12.652660 arp who-has 10.x.x.164 (70:b3:17:e4:70:a8) tell 10.x.x.161

9: 18:26:12.652844 arp reply 10.x.x.164 is-at 70:b3:17:e4:70:a8

10: 18:31:26.273438 arp who-has 10.x.x.164 (70:b3:17:e4:70:a8) tell 10.x.x.161

11: 18:31:26.273621 arp reply 10.x.x.164 is-at 70:b3:17:e4:70:a8

12: 18:36:30.174856 arp who-has 10.x.x.164 (70:b3:17:e4:70:a8) tell 10.x.x.161

13: 18:36:30.175039 arp reply 10.x.x.164 is-at 70:b3:17:e4:70:a8

14: 18:41:45.855790 arp who-has 10.x.x.164 (70:b3:17:e4:70:a8) tell 10.x.x.161

15: 18:41:45.855989 arp reply 10.x.x.164 is-at 70:b3:17:e4:70:a8

15 packets shown

Any help would be gratefully received.

Thanks

James

Chakshu Piplani · ‎01-25-2022

Hi James,

It will be a good idea to look at "sh nat proxy-arp" output to understand if the nat is configured and working as expected.

You can also send a grat arp by running commands:

debug menu ipaddrutl 6 <IP>

Example:

#debug menu ipaddrutl 6 1.1.1.1

Gratuitous ARP sent for 1.1.1.1

Regards,

Chakshu

Do rate helpful posts !

jamesholley · ‎01-25-2022

Thanks Chakshu a useful command.

I do see the right proxy arp entry at the bottom, but cannot work out why I would see proxy arp statements for what are effectively my source remote access networks. Comparing it to the working firewall, this doesn't look right.

hostname/act/pri(config)# sh nat proxy-arp

Nat Proxy-arp Table

id=0x00007fc00ac898b0, ip/id=x.x.109.161, mask=255.255.255.255 ifc=FB_LIMS