Episode 80 - Proxy ARP
Posted by Podcast Team on 12 Nov 2007 9:29 pm. Filed under Podcasts.
Your Hosts: Matt, Bill, DJ, and Ken
* Proxy ARP
- Vista File Limit
- Time Warner Shuts Down Internet
- Virtual Hard Drive Issues
- Ken’s Podcasting Friend
- Teachers Podcasting
- Microsoft Billing Problem
- Feedback
Running time: 57:31
Download Here
On November 13th, 2007 at 9:20 am
Hey guys. Here’s some information from Wikipedia and Cisco on Proxy ARP:
http://www.cisco.com/warp/public/105/5.html
http://en.wikipedia.org/wiki/Proxy_ARP
On November 13th, 2007 at 9:59 am
BTW, you might want to check out the Podcasting for Dummies book that Tee Morris has out. He and Chuck Tomasi from Technorama are working on the next edition. From what I’ve heard, it’s a really great resource for those looking to start a podcast:
http://www.dummies.com/WileyCDA/DummiesTitle/productCd-0471748986,page-1.html
On November 13th, 2007 at 12:08 pm
Comment about the reading books for a podcast, directed toward Bill: Just because you’re NOT selling something doesn’t mean it’s NOT a copyright violation. The fair use doctrine says (in general) that only limited portions may be used, and only for a limited time; if you intend to keep the work, or publish the work (such as in a podcast or in a Powerpoint slideshow) you are SUPPOSED to get written permission.
I read recently that Congress is exploring a more lax definition of fair use to allow for less restrictions on education and not-for-profit use of protected works.
The idea of appropriate use of copyright as relates to technology might be a good podcast topic for the future.
On November 14th, 2007 at 12:52 pm
Spyware/Malware Topic:
1) Try Logging Network activity to File.
netstat -b 5 > NetworkActivity.log
2) Problem sounds like a rootkit Search:
http://www.fantasticfreeware.com/index.php?s=rootkit
McAfee Rootkit Detective
SysProt AntiRootkit
IceSword – Rootkit Detector
Sophos Anti-Rootkit
RootkitRevealer
On November 14th, 2007 at 4:53 pm
This might be an answer as to why your computer is getting on the Internet without a defined default gateway. I had a similar situation, although it happened on a Windows box and it had us baffled for awhile
The explanation turned out to be that the host received an “ICMP Redirect” message from another device. Rather than getting into specifics, if you google ICMP Redirect, you might find the answer to what caused your computer to get on the Internet.
Also, you didn’t mention whether you checked to see if your browser was configured to use a proxy server. As you might know, a proxy server works at the application layer and doesn’t need a default route in order to allow you to access the Internet. Perhaps the host was configured with a valid proxy server entry.
Even if this doesn’t help, I hope to hear what the cause turned out to be.
Cheers
On November 18th, 2007 at 1:45 pm
On the routing issue
Going back to TCPIP basics
A node knows its address and its network. If it tries to connect to a node that is on its network it uses ARP. If it is trying to connect to a node that is not on its network it sends a packet to its default gateway. I don’t see why a node would send an ARP request and thus potentially involve proxy ARP if the target node is not on the source node’s network.
Going way back in my memory I think that it is possible for client nodes to participate in, or at least listen for, routing protocols and use these to determine routes. I used to run a large network that had many triangular paths, ie,
+———B
X |
A + |
Y |
+———C
A, B and C are networks, X and Y are routers.
A node on A can get to a node on C by sending to Y or, if Y is down, by sending to X.
There is a real problem is there is only one “default gateway”. If a node on A must use Y as its default gateway and Y is down then there is no way to “find” X and the alternate path.
We used to do something to PCs so that when the routing protocols determined that Y was unreachable, they would automatically change to using X. I don’t remember what exactly and I don’t have time to dig.
Perhaps your Macs have this functionality enabled by default.
Per the previous comments, I think that ICMP redirects are when a node sends a routing request to its default gateway, if there is a better path to the target node the gateway sends an ICMP Redirect to the client saying “use this router” for further communications which redirects the communications to the new path. I am not sure why this is a problem. If a node does not know about its default gateway then how can that gateway send a redirect to it?
The key functionality is that routers need a way to discover each other and tell each other about state changes and such. These are typically implemented via broadcast protocols so things happen automatically and clients can listen in on these.
Just my guess.
On November 23rd, 2007 at 8:11 pm
With respect to teachers and podcasting. I recently became aware of a tool called “podcast in a box”. It is distributed as an opensource ISO for free use for 30 days. After that you need to buy a mp3 decoder license. I work at a college and see this tool as something our professors could use to quickly get into podcasting. This tool really dumbs down audio capture aspect of podcasting. It can even be setup to auto upload the file to a server of your specification.