[rancid] Rollback functionality and potential pitfalls

Ramon ramonbatwork at gmail.com
Wed Feb 13 15:20:22 UTC 2013

shouldbe, thanks.... that is exactly what I was looking for. Characters "?"
, "$" and "^C" all produce unwanted expansion. The "?" throws a WORD in the
example you cite, breaking the config script. The "$" in a secret or
password string breaks out the clogin process with because it tries to read
it as a variable:

can't read "1": no such variable
    while executing
"subst -nocommands [lindex $commands $i]"
    (procedure "run_commands" line 26)
    invoked from within
"run_commands $prompt $command"
    ("foreach" body line 186)
    invoked from within
"foreach router [lrange $argv $i end] {
    set router [string tolower $router]
    # attempt at platform switching.
    set platform ""
    send_user ..."
    (file "/usr/local/rancid/bin/clogin" line 740)

And the "^C" on the motd enters interactive mode and eventually times out:

#banner login ^C
Enter TEXT message.  End with the character '^'.

Error: TIMEOUT reached

I took the ASA out of the scope yesterday when I noticed what a mess that
would be. So right now I am only trying to make this work for Cisco routers
and switches (2911's and 2950's specifically). Router reload in completely
out of question, and configure replace has proved to be risky at times
(when the command is scripted you have to use force, and it has trimmed
correct vlans and left old ones in place).

I'm going to dig thru clogin code to see if I can come up with a workaround
for the parsing problems mentioned above, any help appreciated!


On Tue, Feb 12, 2013 at 5:49 PM, shouldbe q931 <shouldbeq931 at gmail.com>wrote:

> On Tue, Feb 12, 2013 at 4:04 PM, Ramon <ramonbatwork at gmail.com> wrote:
>> Hello all,
>> I am currently looking in to a way to implement rollback functionality
>> using rancid. What would it take to reverse bad changes and restore the
>> config of a cisco device back to a previous saved version?
>> I ask because just pushing the original config on top of the modified
>> version would not remove or flush out certain statements, possibly leaving
>> duplicates that would have to be removed manually.
>> My first idea was to create a negative file, by generating a "no
>> statement" for every line in the new config that does not match the old
>> config. After pushing the negative file and removing the changes I would
>> push the old config to restore any of the deleted statements.
>> Feedback on any foreseeable issues such as possible hierarchical problems
>> (interfaces, acls, bgp) would be very welcomed.
>> Thanks,
>> Ramon
> A few problems that I thought of
> If you're doing a "conf t" and then sending the updates, you need to be
> able to parse and escape "special" characters, such as the ? in line three
> below
> 1 ip ddns update method dyn.he.net
> 2  HTTP
> 3   add
> http://dynamicrouter.domain.com:hjo97864hhj06hA@ipv4.dyn.dns.he.net/nic/update?hostname=
> <h>&myip=<a>
> The thought of escaping characters lead me onto motd lines...
> banner motd ^C
> This is not the router you are looking for
> ^C
> And finally, the order of NAT rules on an ASA can be critical, this would
> mean either removing all of them (affecting all traffic) and then adding
> all of them, or being able to parse all of the NAT rule lines to add the
> sequence to the rollback, such as
>     no nat 14
>     nat (inside,outside) 14 source static i-server i-server.domain.comservice tcp-in-https tcp-in-https
> I'm sure there are lots of other similar cases
> If you can cope with a reload, then would go with either a tftp boot, or
> erase startup, tftp copy to startup and then reload.
> As well as rancid, I also like to archive to a FTP server, so when TFTP
> isn't an option (such as a remote site router, I can simply go
>  erase start
>  copy ftp://user:pass@host/path/file startup
> And then reload
> For a client that bought CSM, I manage their ASA firewalls with CSM, after
> a particularly bad experience with the built in CSM rollback, I now do the
> changes and deploy normally rather than a rollback deploy if changes need
> to be "reverted".
> Cheers
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.shrubbery.net/pipermail/rancid-discuss/attachments/20130213/57f962fa/attachment.html>

More information about the Rancid-discuss mailing list