On 29/07/2014 19:31, Bryan J Smith wrote: > On Tue, Jul 29, 2014 at 1:19 PM, Martin Møller Skarbiniks Pedersen > <traxpla...@gmail.com <mailto:traxpla...@gmail.com>>wrote: > > On 29 July 2014 18:44, Bryan J Smith <b.j.sm...@ieee.org > <mailto:b.j.sm...@ieee.org>> wrote: > > On Tue, Jul 29, 2014 at 9:50 AM, Martin Møller Skarbiniks > Pedersen <traxpla...@gmail.com <mailto:traxpla...@gmail.com>>wrote: > > 205.1 arp > I don't think it belongs here. And it isn't that useful. > > > Ummm ... isn't that useful? > > I still use it heavily for troubleshooting. > > > Can you tell a bit more about that ? > > > Oh, several uses. > > Bonding is the obvious, first use. Many times one might want to remove > the MAC address from a kernel ARP cache. One of the most common will be > in a cluster environment or IP failover solution. > > But there are many other uses > too. > > E.g., one cannot always bring up tcpdump in some environments > , as going promiscuous on an interface may be outlawed. B > ut one can > easily look > at the kernel's own arp table. > > Heck, on more than one occasion I've needed to verify a > MAC > was accessible via > a reachable port in the same broadcast domain > (some subnet) > on the switch. > I'd be lying if this wasn't because > a network admin > did > not verify something, and I was able to repudiate his statements > showing I could very much see the MAC that wasn't supposed to be there. > > > There are so many other cases where looking at or modifying the kernel's > ARP table is an immediate need or at least useful.
arp is invaluable in network troubleshooting when ifconfig just doesn't cut it anymore. Example, both of these are all too common in mostly-unmanaged environments: - user grabs a static address in a dhcp environment, and it's an allocated address - user powers up a consumer wireless AP to soove a coverage problem and doesn't realize the on-board dhcp is running. both of these are almost impossible to detect without tools like arp -- Alan McKinnon alan.mckin...@gmail.com _______________________________________________ lpi-examdev mailing list lpi-examdev@lpi.org http://list.lpi.org/cgi-bin/mailman/listinfo/lpi-examdev
