From: Daniel Cisco Group Study (danielcgs@imc.net.au)
Date: Wed Feb 26 2003 - 06:35:42 GMT-3
OK,
I've studied this issue in lots of detail..... calculating twos complements etc etc... This has been discussed in quite a lot of detail in previous posts... The conclusion was summarised as per the end of this email. (Brian's section)
I'm still confused about this all... as my own investigations do not quite agree with the consensus when one pref is +ve and another -ve....
Please refer to my debug below:
R9#r
Gateway Using Interval Priority Interface
10.1.5.6 IRDP 4 32 Ethernet0
Default gateway is 10.1.5.6
R9#
GDPclient: 10.1.5.6 via IRDP, interval 4, exp 0x527E84DA, priority 32
R9#
GDPclient: 10.1.5.6 via IRDP, interval 4, exp 0x527E9416, priority 32
R9#
<<<<<R4 comes online with Pref = -31 : >>>>>
GDPclient: 10.1.5.4 initial message
GDPclient: 10.1.5.4 via IRDP, interval 0, exp 0x0, priority -31
GDPclient: 10.1.5.6 via IRDP, interval 4, exp 0x527EA35F, priority 32
R9#
GDPclient: 10.1.5.6 via IRDP, interval 4, exp 0x527EB7D4, priority 32
R9#r
Gateway Using Interval Priority Interface
10.1.5.6 IRDP 4 32 Ethernet0
10.1.5.4 IRDP 14 - 31 Ethernet0
Default gateway is 10.1.5.6
R9#
GDPclient: 10.1.5.6 via IRDP, interval 4, exp 0x527EDB6F, priority 32
GDPclient: 10.1.5.4 via IRDP, interval 13, exp 0x527F33BA, priority -31
.
.
.
A few mintues later:
GDPclient: picked new default router 10.1.5.4
R9#
GDPclient: 10.1.5.4 via IRDP, interval 8, exp 0x5281B239, priority -31
R9#
GDPclient: 10.1.5.6 via IRDP, interval 4, exp 0x5281967E, priority 32
R9#
GDPclient: 10.1.5.6 via IRDP, interval 4, exp 0x5281AACB, priority 32
GDPclient: 10.1.5.4 via IRDP, interval 8, exp 0x5281D12F, priority -31
R9#r
Gateway Using Interval Priority Interface
10.1.5.6 IRDP 5 32 Ethernet0
10.1.5.4 IRDP 8 - 31 Ethernet0
Default gateway is 10.1.5.4
Host Gateway Last Use Total Uses Interface
ICMP redirect cache is empty
But I thought that in this scenario, the +ve value would win????
Can someone shed some light on this one?
Daniel
R9#
-----Original Message-----
From: Brian Dennis [mailto:brian@5g.net]
Sent: Saturday, 13 July 2002 05:14
To: EbonyGuru@aol.com; ccielab@groupstudy.com
Subject: RE: IRDP AGAIN!!
The RFC for IRDP states that the higher values should be preferred but
here's how it works when using a Cisco router as an IRDP client:
If the Cisco router acting as an IRDP client receives two responses from
different IRDP gateways the client will choose the gateway configured
with the lower preference value if they are both positive numbers.
R1#sho ip rout
Gateway Using Interval Priority Interface
10.9.1.7 IRDP 900 200 Ethernet0
10.9.1.6 IRDP 900 2000 Ethernet0
Default gateway is 10.9.1.7
Host Gateway Last Use Total Uses Interface
ICMP redirect cache is empty
R1#
If one gateway has a preference value that is a positive number and one
has a negative number configured for its preference, the client will
choose the gateway with the positive value.
R1#sho ip rout
Gateway Using Interval Priority Interface
10.9.1.7 IRDP 900 200 Ethernet0
10.9.1.6 IRDP 900 - 2000 Ethernet0
Default gateway is 10.9.1.7
Host Gateway Last Use Total Uses Interface
ICMP redirect cache is empty
R1#
If both gateways have negative numbered preference values the Cisco
router acting as an IRDP client will choose the gateway with the lower
preference.
R1#sho ip rout
Gateway Using Interval Priority Interface
10.9.1.7 IRDP 900 - 200 Ethernet0
10.9.1.6 IRDP 900 - 2000 Ethernet0
Default gateway is 10.9.1.6
Host Gateway Last Use Total Uses Interface
ICMP redirect cache is empty
R1#
So to sum it up don't use a Cisco router as an IRDP client ;-)
Brian Dennis, CCIE #2210 (R&S/ISP Dial)
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
EbonyGuru@aol.com
Sent: Friday, July 12, 2002 9:27 AM
To: ccielab@groupstudy.com
Subject: IRDP AGAIN!!
Hi Fellas,
Did we finally decide what the correct config is for this one?
CD says higher preference is better, many of our labs say lower
preference is
the primary gateway.
Does anyone know what the final word is on this please?
TIA,
N'Guru
This archive was generated by hypermail 2.1.4 : Sat Mar 01 2003 - 11:06:36 GMT-3