Question on Ping...?

Unanswered Question
Feb 22nd, 2007

IF i have host A and B.

Host A-1.1.1.1 and HostB 2.2.2.2.

Connected by cross cable or HUB.

When i ping from A to B for what will be the content in ARP request ?

and if Host B reply then A should ping to B.is it ?

I have this problem too.
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shantharam.sury... Thu, 02/22/2007 - 06:23

Hi Ganpat,

Both host should be able to ping each other if there is no firewall.

The below line of yours " When i ping from A to B for what will be the content in ARP request ? " is lil confusing

Regards

S. Shantharam

mheusinger Thu, 02/22/2007 - 06:37

Hi,

the ARP request will contain source MAC of A and destination MAC all FF (broadcast) and in the ARP packet source MAC (A), dest. MAC all 0, source IP 1.1.1.1 destination IP 2.2.2.2

Be aware, that before this happens IP routing in the hosts needs to be configured correctly (check f.e. with "route print" in MS). If host A has no default gateway or routing table entry for 2.2.2.2 then no ARP will be issued. The easiest option will be to set default gateway on both A and B to their own IP address.

Regarding your ICMP (ping) question: the ping command creates an ICMP echo request message and the receiver will reply with an ICMP echo reply message (if not blocked f.e. by firewall).

Hope this helps! Please use the rating system.

Regards, Martin

ganpatspatil Thu, 02/22/2007 - 07:03

Thanks for reply.

If i not configured host with default gateway and no extra routing confi on host(Only ip address are given).

In this situation A will chkk arp chahe and then send ARP request/broadcast to 2.2.2.2.

for this B will reply..........with MAC address........

is it ?

(Is there any thing like ARP broadcast will not goes into antother subnet ?)

mheusinger Thu, 02/22/2007 - 07:40

Hi,

first IP routing takes place in host A, if you ping host B. If from the host A routing table ("route print") the destination is not known (at least through default gateway), then immediately a "destination unreachable" message is issued and no further action is taken. No connectivity, no frames/packets created.

Hope this helps!

Regards, Martin

Danilo Dy Thu, 02/22/2007 - 06:39

When Host A ping Host B, an ARP request is sent at the same time from Host A to Host B. Host A will receive an ARP reply from Host B (even if Host A didn't get and ICMP reply from Host B) no matter what as long as there is a connection. Host A's ARP table will contain the IP Address and MAC address of Host B

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