02-11-2010 11:14 AM - edited 03-06-2019 09:40 AM
Hi,
DHCP Offer is unicasted to the old MAC on the ARP cache. This behaviour is happening as soon as we are connecting 2 or more IP phones in the network with DHCP settings. Avaya support persons have verified all configurations are intact(option 176 etc).
I have checked sniffers for this & it shows that Phone-1 boots in following sequence
1. DHCP Discover in Data Vlan
2. DHCP Offer (IP from Data Vlan 172.16.1.1)
3. ARP Verification
4. DHCP Request (for Data Vlan IP address)
5. DHCP ACK
6. ARP Verification
7. G-ARP.
8. Phone reloads again to get IP in Voice Vlan
9. DHCP Discover in Voice Vlan
10. DHCP Offer (IP from Voice Vlan)
11. ARP Verification
12. DHCP Request (for Voice Vlan IP address)
13. DHCP ACK
14. ARP Verification
15. G-ARP.
When Phone-2 boots
1. DHCP Discover in Data Vlan
2. DHCP Offer (IP from Data Vlan 172.16.1.1 b/c this IP was released by phone-1)
At this stage sniffers clearly show that DHCP-Offer goes to Phone-1's MAC address(172.16.1.1----Phone-1 MAC)....When we see show ip arp on router it shows 172.16.1.1 mapped to phone-1's MAC, after clear this arp entry phone-2 is reloaded & it registers properly using sequence(1-15).
I am wondering why this IP-MAC entry is not getting out when Phone-1 releases the IP to DHCP. It seems to me a bug which might be hitting.
I have tested DHCP stuff by connecting PC in both Data & Voice(by changing it to access vlan) Vlans they are properly getting IP addresses from DHCP, it seems that DHCP relay is also working properly.
Would appreciate if someone is having insight of this.....
Router IOS is c2800nm-advsecurityk9-mz.124-22.T.bin
Regards,
Akhtar
02-11-2010 11:31 AM
Hello Aktar,
I've found an existing bug with same description
CSCsu67864 Bug Details | Bug #35 of 47 | < Previous | Next > |
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DHCP Offer is unicasted to the old MAC on the ARP cache
your IOS image is among affected versions:
>>>12.4(22)T
12.4(22)T1
12.4(22)T2
12.4(22)T3
12.4(22)T4
you need to upgrade to 12.4(24)T
Hope to help
Giuseppe
02-11-2010 11:43 AM
Thanks Giuseppe. Will upgrade the image & check the behaviour.
Regards,
Akhtar
02-14-2010 12:18 AM
got rid of the bug after upgrade. Thanks
Regards,
Akhtar
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