topic Re: How is "pri" calculated automatically by GLBP ? in Switching

How is "pri" calculated automatically by GLBP ?

taoleiccie — Wed, 06 Mar 2019 07:55:13 GMT

Hello.

By using "debug glbp events" can see something like the following

output.

===============================================

GLBP: Fa0/0 123.1 Listen: k/Hello rcvd from lower pri Active router (135/211.102.108.161)

===============================================

GLBP: Fa0/0 123.1 Active: i/Hello rcvd from higher pri Active router (167/211.102.108.152)

===============================================

Note the (xyz / ip_addr)

Is the "xyz" prior to "ip_addr" the priority of the virtual forwarder?

I wonder how this number "xyz" be calculated by router.

Who knows, please?

Thank you.

Re: How is "pri" calculated automatically by GLBP ?

ashok_boin — Tue, 01 Jul 2008 09:50:56 GMT

Hi,

It's not the priority of GLBP which we configured.

I am not sure about 135 or 167 here but what I observed in the labs is...

It says "167" when Primary VF is active & says "135" when Primary VG is inactive.

Pls find the following link which may help...

http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6550/prod_presentation0900aecd801790a3_ps6600_Products_Presentation.html

Regards...

-Ashok.

Re: How is "pri" calculated automatically by GLBP ?

Pravin Phadte — Tue, 01 Jul 2008 09:55:17 GMT

hi,

xyz is calculated in Weighted Load Balancing Algorithm.

It can be as simple as adding all the weight defined and the sum total will be the xyz.

regards,

pravin

Re: How is "pri" calculated automatically by GLBP ?

ashok_boin — Tue, 01 Jul 2008 13:29:07 GMT

Pravin,

I don't think this could be sum of all weights as per debugs.

Pls find the conf & debugs here.

PE-1#sh run | in glbp

glbp 1 ip 20.1.1.10

glbp 1 priority 200

glbp 1 weighting 200

glbp 1 load-balancing weighted

PE-1#debug glbp packets

GLBP Packets debugging is on

PE-1#un all

*Mar 1 00:04:58.831: GLBP: Fa0/0 Grp 1 Hello out VG Active pri 200 vIP 20.1.1

.10 hello 3000, hold 10000 VF 1 Active pri 167 vMAC 0007.b400.0101

*Mar 1 00:04:59.811: GLBP: Fa0/0 Grp 1 Hello in VG Standby pri 50 vIP 20.1.1.

10 hello 3000, hold 10000 VF 2 Active pri 167 vMAC 0007.b400.0102

All possible debugging has been turned off

PE-1#

-------------------------------------------------

PE-2#sh run | in glbp

*Mar 1 00:23:43.679: %SYS-5-CONFIG_I: Configured from console by console

glbp 1 ip 20.1.1.10

glbp 1 priority 50

glbp 1 weighting 150

glbp 1 load-balancing weighted

PE-2#

*Mar 1 00:04:26.279: GLBP: Fa0/0 Grp 1 Hello in VG Active pri 200 vIP 20.1

.10 hello 3000, hold 10000 VF 1 Active pri 167 vMAC 0007.b400.0101

*Mar 1 00:04:27.115: GLBP: Fa0/0 Grp 1 Hello out VG Standby pri 50 vIP 20.1.

10 hello 3000, hold 10000 VF 2 Active pri 167 vMAC 0007.b400.0102

Irrespective of weight configuration, it's giving 167 as Pri.

Regards...

-Ashok.

Re: How is "pri" calculated automatically by GLBP ?

Pravin Phadte — Tue, 01 Jul 2008 14:55:53 GMT

Hi Ashok,

I meant to say that weight algorithm is been used by cisco. This does not have any rfc to prove and calculate.

Weighted allows for GLBP to place a weight on each device when calculating the amount of load sharing. For example, if there are two routers in the group, and router A has twice the forwarding capacity of router B, the weighting value should be configured to be double the amount of router B. To assign a weighting value, the glbp x weighting y, where x is the GLBP group number, and y is the weighting value, a number from 1 to 254.

It would be great if some one can come up with and answer