Are we using ifconfig and netstat? Or are we generation ip and ss now? /me runs ;)
On Tue, Jul 29, 2014 at 1:49 PM, Alan McKinnon <[email protected]> wrote: > On 29/07/2014 19:31, Bryan J Smith wrote: > > On Tue, Jul 29, 2014 at 1:19 PM, Martin Møller Skarbiniks Pedersen > > <[email protected] <mailto:[email protected]>>wrote: > > > > On 29 July 2014 18:44, Bryan J Smith <[email protected] > > <mailto:[email protected]>> wrote: > > > > On Tue, Jul 29, 2014 at 9:50 AM, Martin Møller Skarbiniks > > Pedersen <[email protected] <mailto:[email protected] > >>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 > [email protected] > > _______________________________________________ > lpi-examdev mailing list > [email protected] > http://list.lpi.org/cgi-bin/mailman/listinfo/lpi-examdev
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