[AusNOG] Preferencing Peering BGP over Transit BGP session on Mikrotik

[Joseph Goldman]

The problem in case others face in future was using 'iBGP' in routeros, 
if the 2 routers are the same AS it assumes each router is aware of the 
next-hop IP. In this case the edge router was expected to have a route 
to the Megaport IP Peering range that is actually known on the peering 
router, by telling the peering router to force itself as the next-hop 
choice on the BGP session to his edge router, it allowed the edge router 
to route the traffic correctly. This is still a 'hack-around' to an 
extent, and this is where a good IGP comes in handy to distribute the 
connected routes, so you dont have to 'force-self'. (OSPF usually a 
winner underneath).

Given your comments - is there a programmable difference between eBGP 
and iBGP on any platform? I always thought they are simply terms to put 
into context of use, 2 routers BGP peering with the same AS is 
automatically iBGP by context, vs another AS which is eBGP by context. I 
know platforms (such as RouterOS) treat them differently, but there is 
no 'option' to specify eBGP/iBGP behavior.

On 29/01/15 09:23, Damien Gardner Jnr wrote:
> Ahh, I assumed that was a typo, as I knew he was running iBGP ;)
>
> On 29 January 2015 at 09:21, Andrew Jones <aj at jonesy.com.au 
> <mailto:aj at jonesy.com.au>> wrote:
>
>     Localpref is non-transitive between ASes, so I'm not sure that
>     this would work if Daniel is using eBGP between his peering and
>     edge routers.
>     Daniel,
>     Is there a reason you're running eBGP between your peering and
>     edge routers, rather than iBGP?
>
>
>     On 29.01.2015 08:25, Damien Gardner Jnr wrote:
>
>         Just modify the input filter for the peering session on your
>         peering
>         router to increase the localpref of the received prefixes (BGP
>         Actions
>         - >Set BGP Local Pref - set it to something higher than what
>         you're
>         setting for transit, but lower than what you are setting for
>         prefixes
>         received from your customers). As long as you're not modifying the
>         localpref of prefixes received from the peering router on your
>         edge
>         router, then it'll accept that, and you'll see traffic go to
>         peering
>         rather than transit.
>
>         On 29 January 2015 at 08:21, Daniel <daniel at dwatson.me
>         <mailto:daniel at dwatson.me>> wrote:
>
>             Hi Guys
>
>             As some people on-list may be aware ive switched from
>             Vyatta/VyOS to
>             Mikrotik as its much easier for me to manage then all the
>             issues i
>             previously had with Vyatta/VyOS,
>
>             Since switching across to Mikrotik ive not had any issues
>             what so ever
>             except until now,
>
>             We have MegaPort terminated to our peering router, in
>             which I have a ebgp
>             session configured between the peering router and our edge
>             router,
>
>             However when i traceroute 8.8.8.8 it still seems to be
>             going over transit
>             than peering,
>
>             I was wondering if somebody on-list whom might have 10 -
>             15minutes spare
>             could give me a hand to resolve this issue?
>
>             Please let me know and ill be more then happy to provide
>             further
>             information on request.
>
>             TIA
>
>             Daniel
>
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>
>         --
>
>         Damien Gardner Jnr
>         VK2TDG. Dip EE. GradIEAust
>         rendrag at rendrag.net <mailto:rendrag at rendrag.net> -
>         http://www.rendrag.net/ [2]
>         --
>         We rode on the winds of the rising storm,
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>
> -- 
>
> Damien Gardner Jnr
> VK2TDG. Dip EE. GradIEAust
> rendrag at rendrag.net <mailto:rendrag at rendrag.net> - 
> http://www.rendrag.net/_
> _--
> We rode on the winds of the rising storm,
>  We ran to the sounds of thunder.
> We danced among the lightning bolts,
>  and tore the world asunder
>
>
>
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