[Rstplib-users] RE: 802.1w: double flushing in simplest case ?

[Vipin J. <vi...@te...>]

Albina,

RSTP or bridging does not interfere with routing function. I suspect
that you are talking about a bridge-router (brouter as it used to be
called). RSTP is a no-op in a pure router.

In a brouter, you do not need to unresolve ARP entries or next hop
information. Typically, you would have a number of bridged ports (part
of the same layer 2 domain) and an IP interface (virtualized) sitting on
top of each such set of ports. Next hop in a routing table will point to
this virtual IP interface as the outbound interface. ARP resolution is
also above the bridging function and hence does not need to change
irrespective of what happens to bridge ports in the domain. All it means
is that a packet will be submitted to an appropriate IP interface for
forwarding, you also know the MAC address of next hop router, just do
not know which physical (bridge) port the packet should go out of.
Because addresses have been flushed on these bridge ports, such a packet
will be flooded in the corresponding layer 2 domain.

Of course, if you change the IP address to MAC address association for a
device, no bridging will help you. That's why you have mechanisms such
as gratuitous ARP (all layer 3 functions).

Hope it helps.

Vipin

-----Original Message-----
From: Albina Krigma-Lee [mailto:alb...@ya...]
Sent: Thursday, January 03, 2002 7:23 AM
To: Tony Jeffree
Cc: std...@ie...; rst...@li...
Subject: Re: 802.1w: double flushing in simplest case ?



I see, but it seems that learning entries
flushing/ageing must unresolve ARP entries and
NextHops in FIB. So I quess, the double
flushing could be really expencive cost of RSTP.
Or Alex isn't right ?
Sincerely, Albina Krigma-Lee

 --- Tony Jeffree <to...@je...> wrote:
> The RSTP standard defines the operation of RSTP
> bridges - it has nothing to=20
> say on the subject of routers.
>=20
> Regards,
> Tony
>=20
> At 00:05 04/01/2002 +1100, Albina Krigma-Lee wrote:
>=20
> >Hi All,
> >If RSTP operates in a router and makes flush()
> >function, do it have to delete Forwarding
> Information
> >Base (FIB) entries too ?
> >
> >Thanks in advance, albina
> >
> >
> >http://my.yahoo.com.au - My Yahoo!
> >- It's My Yahoo! Get your own!
>=20
> =20

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