[quagga-users 14437] Re: Redundant Service IP on loopback

Dave Hall kdhall at binghamton.edu
Wed Sep 28 03:05:51 BST 2016


Moacir,


So I'm glad that I wasn't imagining that I saw this somewhere. However, 
some sort of cookbook would be a nice way to get started for the first 
time I deploy something like this.  I've paged through some Quagga docs 
and there's a lot there for someone who's not looking to become an 
expert, even in the BGP section.  (I would like to be an expert, but not 
just yet.)


I'm also thinking that there might be some Linux sysctl values that need 
to set correctly.


Do you know of any example configs I could study?


Thanks.


-Dave

-- 
Dave Hall
Binghamton University
kdhall at binghamton.edu
607-760-2328 (Cell)
607-777-4641 (Office)

On 9/27/16 8:43 AM, Moacir Ferreira wrote:
>
> Hey Dave,
>
>
> You gave the whole answer on your question... You need to:
>
>
> 1 - Create a loopback interface making sure your services (DNS, FTP, 
> HTTP, NTP, etc.) will also run in this IP address;
>
> 2 - Run a routing protocol (it can be BGP or OSPF, but I find it 
> easier using OSPF unless facing the Internet for some reason); I would 
> also recommend using Quagga that you can install via apt-get or yum 
> install;
>
> 3 - Announce your /32 loopback IP address on the routing protocol that 
> you are using;
>
> 4 - Manipulate the rounting protocol on each server (in BGP increase 
> preference or AS path; in OSPF increase interface cost), so one of the 
> servers will be preferred; the manipulation can also be done at the 
> router/switch the servers are connected to;
>
>
> Done!
>
>
> By the way, this is becoming a very popular way for high availability. 
> However, care must be taken should you need to synchronize data in 
> between the two servers. If you need to keep them in sync, use the 
> Ethernet IP address to do so (not the loopback address) and everything 
> will go quite smooth.
>
>
> As you need server redundancy, VRRP (HSRP) is not a solution for this. 
> Unless you are willing to "complicate", anycast is really a bad choice.
>
>
> Cheers!
>
> Moacir
>
>
>
> ------------------------------------------------------------------------
> *From:* Dave Hall <kdhall at binghamton.edu>
> *Sent:* Tuesday, September 27, 2016 5:02 AM
> *To:* quagga-users at lists.quagga.net
> *Subject:* [quagga-users 14432] Redundant Service IP on loopback
> Hello,
>
> I found a link about this a couple months ago but apparently I didn't
> save it, so I'm going to have to ask...
>
> The article I found described how to set up the IP for some service
> (i.e. DNS) on the loopback interface of two identical servers and then
> use BGP to distribute route advertisements with different metrics such
> that if the server with the lower metric fails or is rebooted the
> traffic will go to the other server.
>
> My main goal here is services such as DNS and LDAP were the service is
> primarily used by other hosts/servers on the same subnet.  I'm not sure
> if the original scheme (above) assumed that there was a router involved,
> but in this case there is no router.
>
> Any guidance would be sincerely appreciated.
>
> Thanks.
>
> -Dave
>
>
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