Hi Team ,
As far as i know that G arp will used in two senarios in DHCP and HSRP .
In HSRP:
HSRP enabled routers use a virtual MAC address. The active HSRP router will take ownership of that MAC address and the downstream switch will use it in its CAM table. So from the switch's perspective, it will forward frames out of the port connected to the active router. If the active HSRP router fails, the standby router takes ownership of the virtual MAC address, but it needs a way to inform the switch that it now should forward all frames for that MAC address to the standby router. This is accomplished with a gratuitous ARP. The standby router will send a gratuitous ARP to the switch letting it know that it should forward frames for the virtual MAC address to itself instead of the router that failed.
When the standby routers send the G- ARP to the switch ARP packet contains the below as per me
Source Ip: Standby router IP [10.10.2.1]
Source MAC: Standby router MAC
Destination IP: Standby router IP [10.10.2.1] or Broadcast IP ??
Destination MAC: Standby router MAC or Broadcast MAC??
I just want to know what would be the destination IP and Destination MAC in the ARP Packet ??
In DHCP:
After receiving the IP address from the DHCP. The connecting computer can not be sure that the newly handed out IP-address from the DHCP sever can be used before asking all the other computers on the network. This is because the DHCP server have no control over computers that have been manually assigned static IP-addresses. The connecting computer have to send out a "provoking" ARP (Gratuitous ARP) packet, claiming the IP-address. If another computer already uses this IP-address it has to send out a "already in use" ARP packet defending its IP-address and letting the connecting computer know that this address are already in use. If the IP-address is already in use - If the IP-address is already in use by another computer the connecting computer can not use the IP-address handed out by the DHCP server and will inform the DHCP server by sending a DHCP-DECLINE packet letting the DHCP server know that the connecting computer do not accept this address. Then the connecting computer will start all over again, finding a DHCP server and then ask for a IP-address.
In this G ARP request packet .
Source IP : PC ip
Source MAC : PC MAC
Destination IP : PC IP
Destination MAC : broadcast MAC.
If it recieves the ARP Reply then it will consider that this IP is alread in use and will send decline message to DHCP server.
Kindly let me know whether my understanding is correct in case of DHCP
Sorry for such a long notes here .
Thanks in advance
Regards ,
Vidiya
As far as i know that G arp will used in two senarios in DHCP and HSRP .
In HSRP:
HSRP enabled routers use a virtual MAC address. The active HSRP router will take ownership of that MAC address and the downstream switch will use it in its CAM table. So from the switch's perspective, it will forward frames out of the port connected to the active router. If the active HSRP router fails, the standby router takes ownership of the virtual MAC address, but it needs a way to inform the switch that it now should forward all frames for that MAC address to the standby router. This is accomplished with a gratuitous ARP. The standby router will send a gratuitous ARP to the switch letting it know that it should forward frames for the virtual MAC address to itself instead of the router that failed.
When the standby routers send the G- ARP to the switch ARP packet contains the below as per me
Source Ip: Standby router IP [10.10.2.1]
Source MAC: Standby router MAC
Destination IP: Standby router IP [10.10.2.1] or Broadcast IP ??
Destination MAC: Standby router MAC or Broadcast MAC??
I just want to know what would be the destination IP and Destination MAC in the ARP Packet ??
In DHCP:
After receiving the IP address from the DHCP. The connecting computer can not be sure that the newly handed out IP-address from the DHCP sever can be used before asking all the other computers on the network. This is because the DHCP server have no control over computers that have been manually assigned static IP-addresses. The connecting computer have to send out a "provoking" ARP (Gratuitous ARP) packet, claiming the IP-address. If another computer already uses this IP-address it has to send out a "already in use" ARP packet defending its IP-address and letting the connecting computer know that this address are already in use. If the IP-address is already in use - If the IP-address is already in use by another computer the connecting computer can not use the IP-address handed out by the DHCP server and will inform the DHCP server by sending a DHCP-DECLINE packet letting the DHCP server know that the connecting computer do not accept this address. Then the connecting computer will start all over again, finding a DHCP server and then ask for a IP-address.
In this G ARP request packet .
Source IP : PC ip
Source MAC : PC MAC
Destination IP : PC IP
Destination MAC : broadcast MAC.
If it recieves the ARP Reply then it will consider that this IP is alread in use and will send decline message to DHCP server.
Kindly let me know whether my understanding is correct in case of DHCP
Sorry for such a long notes here .
Thanks in advance
Regards ,
Vidiya
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