bgp as-override and remove private as seems to be not working

RouterOS Forwarding Protocols
1

Hi all,…
I have build up the follwing lab:

CE1 (AS65533)-----ebgp—>PE1(AS100)----->P1---->PE2(AS100)----ebgp---->CE2(AS200)


At CE1 I inject a route 172.16.1.0/24 and export ist to PE1....  --> Works fine in first step..
PE1 gives the route to PE2 via ibgp --> works fine as well
PE2 gives the route to CE2 ---- Well done!!! Route is seen, Controlplane works well.

Now:
I have tried the remove private as feature as well as the as-override feature configured at PE1 at the ebgp session towards CE1.
But nothing happend. The route attributes are always the same logged at PE2.
See:
Without any route-manipulation on PE2:
[lab@PE2] > routing/route/print detail where dst-address=172.16.1.0/24
Flags: X - disabled, F - filtered, U - unreachable, A - active;
c - connect, s - static, r - rip, b - bgp, o - ospf, d - dhcp, v - vpn, m - modem, a - ldp-address, l - ldp-mapping, y - copy;
H - hw-offloaded; + - ecmp, B - blackhole
Ab   afi=ip4 contribution=active dst-address=172.16.1.0/24
routing-table=main gateway=192.168.1.1
immediate-gw=192.168.100.1%ether1 distance=200 scope=40
target-scope=30 belongs-to="bgp-IP-10.0.0.2"
bgp.peer-cache-id=*B000002 .as-path="65533" .local-pref=100
.atomic-aggregate=yes .origin=igp
debug.fwp-ptr=0x202822A0
[lab@PE2] >

With as-override configured towards CE-1:
[lab@PE2] > routing/route/print detail where dst-address=172.16.1.0/24
Flags: X - disabled, F - filtered, U - unreachable, A - active;
c - connect, s - static, r - rip, b - bgp, o - ospf, d - dhcp, v - vpn, m - modem, a - ldp-address, l - ldp-mapping, y - copy;
H - hw-offloaded; + - ecmp, B - blackhole
Ab   afi=ip4 contribution=active dst-address=172.16.1.0/24
routing-table=main gateway=192.168.1.1
immediate-gw=192.168.100.1%ether1 distance=200 scope=40
target-scope=30 belongs-to="bgp-IP-10.0.0.2"
bgp.peer-cache-id=*B000002 .as-path="65533" .local-pref=100
.atomic-aggregate=yes .origin=igp
debug.fwp-ptr=0x202822A0
[lab@PE2] >

With remove "private as" from PE1 towards ebgp to CE1
[lab@PE2] > routing/route/print detail where dst-address=172.16.1.0/24
Flags: X - disabled, F - filtered, U - unreachable, A - active;
c - connect, s - static, r - rip, b - bgp, o - ospf, d - dhcp, v - vpn, m - modem, a - ldp-address, l - ldp-mapping, y - copy;
H - hw-offloaded; + - ecmp, B - blackhole
Ab   afi=ip4 contribution=active dst-address=172.16.1.0/24
routing-table=main gateway=192.168.1.1
immediate-gw=192.168.100.1%ether1 distance=200 scope=40
target-scope=30 belongs-to="bgp-IP-10.0.0.2"
bgp.peer-cache-id=*B000002 .as-path="65533" .local-pref=100
.atomic-aggregate=yes .origin=igp
debug.fwp-ptr=0x202822A0
[lab@PE2] >

As you can see--->  always the same .as-path="65533" is showen at the output.
Did I something wrong or is this a bug ?

I have tried this configuration with RouterOS 7.5 and RouterOS7.6rc1 (Because of the BGP-advertised feature).. always the same.

Thank you for your time community...

Andreas
2

Currently as-override and some other AS Hacks are not fully implemented.

3

Thank you for fast answering my question.
Was my idea of configuration correct? Yes?

Is “remove-private-as” or “next-hop-self” not implemented as well?

Does anybody think it is possible to publish a list of feature that doesn’ t work at the moment?
Is is really frustrating to check this by try and error.

If I switch back to any RouterOS version 6.anything, will it work then ?

:wink: A.

4

So remove-private-as=yes isn’t working in 7.7b6. Hopefully this is one of the ‘hacks’ that will get fixed soon, no?

5

We tried to replace a lot of ccr1072 (6.49) with ccr2216 (7.6). The missing AS Override makes the new ccr2216 routers useless for BGP. This is a must have feature in all larger setups. No idea why this simple thing is missing on the flagship router.

6

Hi MT Community,

just stumbled across the same issue today, as my Transit Provider is filtering all received routes with private ASNs in the path.

remote-private-as would have been the solution, but it doesn’t seem to work.
as-override as a workaround could have been possible (not great, but anyways) , but it doesn’t seem to work as well.
as-path is not writeable in routing/filter/rules, so manually changing via filter is not possible as well.

The only solution i could find so far is manually adding static routes for these subnets (luckily not a lot so far in my case).

Did anyone find a better / nicer solution so far?

I checked 7.7 stable and 7.8 testing changelog, but it doesn’t look like a quick fix will be available quite soon.

Thanks,
Stephan

7

Hi everyone,

I found the solution to this issue. It seems like you have to enable remove private AS on the client side and not on the ISP side.

I’m using routerOs V7.16