RE: How does Internal Bypass mode work on Juniper IDP range

That must have been annoying.  Luckily I'm pretty sure we haven't run into =
an obscure Juniper bug, as the hardware bypass engaged and disengaged corre=
ctly according to syslog and our observations.  It was more about the effec=
ts of hardware bypass on the surrounding network environment.

Thanks

-----Original Message-----
From: Fairtel - Barry Hofland [mailto:[email protected]]=20
Sent: 26 October 2010 22:33
To: Maqbool Hashim
Cc: [email protected]
Subject: Re: How does Internal Bypass mode work on Juniper IDP range

Hi,

Although not an expert let me share my experiences. Even in a transparent m=
ode the IDP works the packets through different buffers and memory spaces t=
o subject the traffic to whatever you configured in NSM. In a rare occasion=
 my customer managed to trigger a bug that caused a buffer to fill up but n=
ot release any traffic causing the IDP to crash. Which in its turn did not =
trigger the fail open ( act like a wire if broken or out of power ). Then y=
ou will notice something similar to what you are experiencing.=20

The challenge is to reproduce the crash and have juniper's TAC assess what'=
s wrong.=20

Only if you are also a customer running a very rare bug of course.=20

Good luck.=20

Barry Hofland

Op 26 okt. 2010 om 18:29 heeft Maqbool Hashim <[email protected]> het vol=
gende geschreven:

> Hi,
>=20
> I recently saw an outage in a network that had a Juniper IPS device deplo=
yed.  The outage consisted of tcp sessions timing out for users, ping conne=
ctivity was not confirmed.  The IPS is deployed in transparent mode and Int=
ernal Bypass is enabled on the ingress and egress interface pair that make =
up the virtual router.   My understanding of the internal bypass feature is=
 as follows as per the Juniper documentation:
>=20
> In bypass mode, traffic enters the IDP ingress port and is forwarded out =
of the egress interface without being passed to the IDP engine.  The ingres=
s and egress interface join mechanically to form a circuit in order to cont=
inue passing traffic through the IPS device.  Effectively the interfaces be=
come a piece of wire.  Bypass mode is triggered by a timing mechanism durin=
g system failure or shutdown.  This feature has been enabled to optimise av=
ailability and ensure that network outages do not occur because the IDS cra=
shes/fails/ or cannot process packets fast enough.
>=20
> I'm trying to determine the cause of the outage we suffered, which is why=
 I wanted a deeper understanding of internal bypass and the effects it may =
or may not have on the surrounding network architecture.  The outage I saw =
occurred at around the same time the IPS box rebooted and consequently ente=
red bypass mode.  Bypass mode was only activated for a minute from the sysl=
og entries, however the outage we saw lasted for approximately half an hour=
.=20
>=20
> So my questions regarding bypass mode are:
>=20
> 1) During bypass mode the link status on the IPS interfaces will be down.=
  Will the switch interfaces connected to the IPS device remain up as they =
are now connected to each other through the IPS (piece of wire) rather than=
 to the IPS interfaces?
>=20
> 2)  If the switch interfaces are now connected to each other rather than =
the IPS what about mac forwarding tables?  Is it possible that the forwardi=
ng tables on the switches get confused?
>=20
> 3) Any specific session based issues that could be caused by the IPS devi=
ce engaging and disengaging internal bypass mode?
>=20
> My feeling is that the issues might be caused by how the network environm=
ent responds to the IPS engaging/disengaging internal bypass mode rather th=
an an issue with the IPS device.  I'm just looking for some guidance on any=
 gotchas that I should be aware of with regards to the network environment =
when the IPS device triggers bypass mode.
>=20
> Thanks
>=20
> Maq
>=20
>=20
>=20
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