Ethernet Switching
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Ethernet Switching

FYI: EX switch dhcp snooping bindings persistence 11.4 -> 12.3

[ Edited ]
‎08-26-2013 08:13 AM

hi,

 

In another post I have discussed how to set dhcp-snooping-file location to persist Junos upgrade (11.4R5.5 to 11.4R5.7)

AFAIK, currently  there is no recommendation for 'dhcp-snooping-file location' in the documentation. Setting it to /var/home/filename worked with 11.4R5.5 to 11.4R5.7 upgrade.

 

Recently upgraded a few switches from 11.4R5.7 to 12.3R3.4. It looks like the format of dhcp-snooping-file has changed and all bindings are lost during upgrade. I don't see any warnings in the release notes/docs.

 

After reboot, dhcp snooping statistics shows Failed Record Reads = 1 and some Successful Record Reads

 

admin@EX> show dhcp snooping statistics
DHCP Snoop Persistence statistics
Successful Remote Transfers: 0           Failed Remote Transfers: 0
Successful Record Reads    : 50          Failed Record Reads    : 1
Successful Record Writes   : 0           Failed Record Writes   : 0                    

It's not true, all records are lost

 

11.4R5.7 dhcp-snooping-file  file format:

 

admin@EX> file show /var/home/DB-dhcp-snooping
Version : 1
00:13:77:ac:xx:yy       10.33.20.191    Fri Aug 23 13:53:47 2013        ge-0/0/46.0     VLAN1    4ab41210 82af7ad4 fb706b44 460c3fd3
00:14:c2:e1:zz:ww       10.33.20.165    Fri Aug 23 13:53:47 2013        ge-0/0/46.0     VLAN1    8fa8a58a e86725e9 be7bee73 a7239368

12.3R3.4 - please notice extra column added (positive/negative integer):

 

admin@EX> file show /var/home/DB-dhcp-snooping
Version : 1
00:1e:33:54:xx:yy       10.33.20.148    Fri Aug 23 14:19:15 2013        ge-0/0/41.0     VLAN1    1375559649      75eebcf9 5fb2809f 32808538 586c9175
00:1e:68:a2:zz:ww       10.33.20.4      Fri Aug 23 14:06:26 2013        ge-0/0/46.0     VLAN1    -447439395      4099bb8b 1dd5fbb0 4b1e3f36 b344865e

 

To make the upgrades painless, we had to disable arp-inspection and/or ip-source-guard before upgrade (and enable it once dhcp-snooping database is populated with new entries).

 

Is to possible to have true dhcp snooping bindings persistence on EX switches ? I mean persistence in case of device restart and Junos upgrades. What is see currently is a feature or a bug ?

 

Be careful with any Junos upgrade if you have dhcp-snooping enabled.

jtb