<HTML ><HEAD ><TITLE >Common Problems</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ "><LINK REL="HOME" TITLE="Bridging mini-HOWTO" HREF="index.html"><LINK REL="PREVIOUS" TITLE="Setup" HREF="x23.html"><LINK REL="NEXT" TITLE="Copyright" HREF="x149.html"></HEAD ><BODY CLASS="SECT1" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >Bridging mini-HOWTO</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="x23.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="x149.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="AEN72">2. Common Problems</H1 ><DIV CLASS="QANDASET" ><DL ><DT >Q: <A HREF="x72.html#AEN76" >I get the message <SPAN CLASS="ERRORNAME" >ioctl(SIOCGIFBR) failed: Package not installed </SPAN >. What does this mean?</A ></DT ><DT >Q: <A HREF="x72.html#AEN83" >Machines on one side cannot ping the other side!</A ></DT ><DT >Q: <A HREF="x72.html#AEN99" >I cannot <SPAN CLASS="APPLICATION" >telnet</SPAN >/<SPAN CLASS="APPLICATION" >ftp</SPAN > from the bridge! Why?</A ></DT ><DT >Q: <A HREF="x72.html#AEN106" >What do I need to set up in the way of routing?</A ></DT ><DT >Q: <A HREF="x72.html#AEN113" >The bridge appears to work, but why doesn't <SPAN CLASS="APPLICATION" >traceroute</SPAN > show the bridge as a part of the path?</A ></DT ><DT >Q: <A HREF="x72.html#AEN120" >Is it necessary to compile <TT CLASS="ENVAR" >IP_FORWARD</TT > into the kernel?</A ></DT ><DT >Q: <A HREF="x72.html#AEN127" >Why are the physical ethernet addresses for port 1 and port 2 the same according to the <SPAN CLASS="APPLICATION" >brcfg</SPAN > program? Shouldn't they be different?</A ></DT ><DT >Q: <A HREF="x72.html#AEN133" >Bridging does not appear to be an option when performing a make config on the kernel. How does one enable it?</A ></DT ><DT >Q: <A HREF="x72.html#AEN140" >Too many hubs (4 or more) are chained one after another in series, cause timing problems on an ethernet. What effect does a bridge have in a subnet that is layered with hubs?</A ></DT ><DT >Q: <A HREF="x72.html#AEN145" >Can a bridge interface to both 10Mb and 100Mb ethernet segments? Will such a configuration slow down the rest of the traffic on the high speed side?</A ></DT ></DL ><DIV CLASS="QANDAENTRY" ><DIV CLASS="QUESTION" ><P ><A NAME="AEN76"><B >Q: </B >I get the message <SPAN CLASS="ERRORNAME" >ioctl(SIOCGIFBR) failed: Package not installed </SPAN >. What does this mean?</P ></DIV ><DIV CLASS="ANSWER" ><P ><B >A: </B >You don't have bridging capability in your kernel. Get a 2.0 or greater kernel, and recompile with the <TT CLASS="ENVAR" >BRIDGING</TT > option enabled.</P ></DIV ></DIV ><DIV CLASS="QANDAENTRY" ><DIV CLASS="QUESTION" ><P ><A NAME="AEN83"><B >Q: </B >Machines on one side cannot ping the other side!</P ></DIV ><DIV CLASS="ANSWER" ><P ><B >A: </B ><LI ><SPAN >Did you enable bridging using <SPAN CLASS="APPLICATION" >brcfg -ena</SPAN >? (<SPAN CLASS="APPLICATION" >brcfg</SPAN > should say <SPAN CLASS="RETURNVALUE" >bridging is ENABLED</SPAN >)</SPAN ></LI ><LI ><SPAN >Did you put the interfaces into promiscuous mode? (issue the <SPAN CLASS="APPLICATION" >ifconfig</SPAN > command. The <SPAN CLASS="PROPERTY" >PROMISC</SPAN > flag should be on for both interfaces.)</SPAN ></LI ><LI ><SPAN >If using multiple-media interface adapters, make sure that the correct one is enabled. You may need to use the config/setup program that came with the network interface card.</SPAN ></LI ></P ></DIV ></DIV ><DIV CLASS="QANDAENTRY" ><DIV CLASS="QUESTION" ><P ><A NAME="AEN99"><B >Q: </B >I cannot <SPAN CLASS="APPLICATION" >telnet</SPAN >/<SPAN CLASS="APPLICATION" >ftp</SPAN > from the bridge! Why?</P ></DIV ><DIV CLASS="ANSWER" ><P ><B >A: </B >This is because there is no IP address bound to any of bridge interfaces. A bridge is to be a transparent part of a network.</P ></DIV ></DIV ><DIV CLASS="QANDAENTRY" ><DIV CLASS="QUESTION" ><P ><A NAME="AEN106"><B >Q: </B >What do I need to set up in the way of routing?</P ></DIV ><DIV CLASS="ANSWER" ><P ><B >A: </B >Nothing! All routing intelligence is handled by the bridging code in the kernel. To see the ethernet addresses as they are learned by the bridge, use the <SPAN CLASS="APPLICATION" >brcfg</SPAN > program in debug mode:</P ><TABLE BORDER="1" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="SCREEN" >brcfg -deb </PRE ></FONT ></TD ></TR ></TABLE ></DIV ></DIV ><DIV CLASS="QANDAENTRY" ><DIV CLASS="QUESTION" ><P ><A NAME="AEN113"><B >Q: </B >The bridge appears to work, but why doesn't <SPAN CLASS="APPLICATION" >traceroute</SPAN > show the bridge as a part of the path?</P ></DIV ><DIV CLASS="ANSWER" ><P ><B >A: </B >Due to the nature of a bridge, a <SPAN CLASS="APPLICATION" >traceroute</SPAN > should NOT show the bridge as a part of the path. A bridge is to be a transparent component of the network.</P ></DIV ></DIV ><DIV CLASS="QANDAENTRY" ><DIV CLASS="QUESTION" ><P ><A NAME="AEN120"><B >Q: </B >Is it necessary to compile <TT CLASS="ENVAR" >IP_FORWARD</TT > into the kernel?</P ></DIV ><DIV CLASS="ANSWER" ><P ><B >A: </B >No. The bridging code in the kernel takes care of the packet transport. <TT CLASS="ENVAR" >IP_FORWARD</TT > is for a gateway that has IP addresses bound to its interfaces.</P ></DIV ></DIV ><DIV CLASS="QANDAENTRY" ><DIV CLASS="QUESTION" ><P ><A NAME="AEN127"><B >Q: </B >Why are the physical ethernet addresses for port 1 and port 2 the same according to the <SPAN CLASS="APPLICATION" >brcfg</SPAN > program? Shouldn't they be different?</P ></DIV ><DIV CLASS="ANSWER" ><P ><B >A: </B >No. Every port on a bridge intentionally is assigned the same physical ethernet address by the bridging code.</P ></DIV ></DIV ><DIV CLASS="QANDAENTRY" ><DIV CLASS="QUESTION" ><P ><A NAME="AEN133"><B >Q: </B >Bridging does not appear to be an option when performing a make config on the kernel. How does one enable it?</P ></DIV ><DIV CLASS="ANSWER" ><P ><B >A: </B >During the kernel config, answer <SPAN CLASS="QUOTE" >"Y"</SPAN > to the question, <TT CLASS="PROMPT" >Prompt for development and/or incomplete code/drivers (CONFIG_EXPERIMENTAL) [Y/n/?]</TT >.</P ></DIV ></DIV ><DIV CLASS="QANDAENTRY" ><DIV CLASS="QUESTION" ><P ><A NAME="AEN140"><B >Q: </B >Too many hubs (4 or more) are chained one after another in series, cause timing problems on an ethernet. What effect does a bridge have in a subnet that is layered with hubs?</P ></DIV ><DIV CLASS="ANSWER" ><P ><B >A: </B >A bridge resets the 3/4/5 hubs rule. A bridge does not deal with packets the way a hub does, and is therefore not a contributor to timing problems on a network.</P ></DIV ></DIV ><DIV CLASS="QANDAENTRY" ><DIV CLASS="QUESTION" ><P ><A NAME="AEN145"><B >Q: </B >Can a bridge interface to both 10Mb and 100Mb ethernet segments? Will such a configuration slow down the rest of the traffic on the high speed side?</P ></DIV ><DIV CLASS="ANSWER" ><P ><B >A: </B >Yes, a bridge can tie together a 10Mb segment with a 100Mb segment. As long as the network card on the fast network is 100Mb capable, TCP takes care of the rest. While it's true that the packets from a host in the 100Mb network communicating to a host in the 10Mb network are moving at only 10Mb/s, the rest of the traffic on the fast ethernet is not slowed down.</P ></DIV ></DIV ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="x23.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="x149.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Setup</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" > </TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Copyright</TD ></TR ></TABLE ></DIV ></BODY ></HTML >