Olaf Kirch - Linux Network Administrator Guide, Second Edition

PLIP provides a way to send IP datagrams across a parallel port connection. It is mostly used to communicate with PCs running DOS. On typical PC hardware, PLIP can be faster than PPP or SLIP, but it requires much more CPU overhead to perform, so while the transfer rate might be good, other tasks on the machine may be slow.

The following questions address network cards from various vendors. As more drivers are being developed, you are likely to see questions added to this section. If you want to build a kernel you can use on a number of different machines, or if your machine has more than one type of network card installed, you can enable more than one driver:

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Ethernet (10 or 100Mbit) (CONFIG_NET_ETHERNET) [Y/n/?]

3COM cards (CONFIG_NET_VENDOR_3COM) [Y/n/?]

3c501 support (CONFIG_EL1) [N/y/m/?]

3c503 support (CONFIG_EL2) [N/y/m/?]

3c509/3c579 support (CONFIG_EL3) [Y/m/n/?]

3c590/3c900 series (592/595/597/900/905) "Vortex/Boomerang" support (CONFIG_VORTEX) [N/y/m/?]

AMD LANCE and PCnet (AT1500 and NE2100) support (CONFIG_LANCE) [N/y/?]

AMD PCInet32 (VLB and PCI) support (CONFIG_LANCE32) [N/y/?] (NEW)

Western Digital/SMC cards (CONFIG_NET_VENDOR_SMC) [N/y/?]

WD80*3 support (CONFIG_WD80x3) [N/y/m/?] (NEW)

SMC Ultra support (CONFIG_ULTRA) [N/y/m/?] (NEW)

SMC Ultra32 support (CONFIG_ULTRA32) [N/y/m/?] (NEW)

SMC 9194 support (CONFIG_SMC9194) [N/y/m/?] (NEW)

Other ISA cards (CONFIG_NET_ISA) [N/y/?]

Cabletron E21xx support (CONFIG_E2100) [N/y/m/?] (NEW)

DEPCA, DE10x, DE200, DE201, DE202, DE422 support (CONFIG_DEPCA) [N/y/m/?] (NEW)

EtherWORKS 3 (DE203, DE204, DE205) support (CONFIG_EWRK3) [N/y/m/?] (NEW)

EtherExpress 16 support (CONFIG_EEXPRESS) [N/y/m/?] (NEW)

HP PCLAN+ (27247B and 27252A) support (CONFIG_HPLAN_PLUS) [N/y/m/?] (NEW)

HP PCLAN (27245 and other 27xxx series) support (CONFIG_HPLAN) [N/y/m/?] (NEW)

HP 10/100VG PCLAN (ISA, EISA, PCI) support (CONFIG_HP100) [N/y/m/?] (NEW)

NE2000/NE1000 support (CONFIG_NE2000) [N/y/m/?] (NEW)

SK_G16 support (CONFIG_SK_G16) [N/y/?] (NEW)

EISA, VLB, PCI and on card controllers (CONFIG_NET_EISA) [N/y/?]

Apricot Xen-II on card ethernet (CONFIG_APRICOT) [N/y/m/?] (NEW)

Intel EtherExpress/Pro 100B support (CONFIG_EEXPRESS_PRO100B) [N/y/m/?] (NEW)

DE425, DE434, DE435, DE450, DE500 support (CONFIG_DE4X5) [N/y/m/?] (NEW)

DECchip Tulip (dc21x4x) PCI support (CONFIG_DEC_ELCP) [N/y/m/?] (NEW)

Digi Intl. RightSwitch SE-X support (CONFIG_DGRS) [N/y/m/?] (NEW)

Pocket and portable adaptors (CONFIG_NET_POCKET) [N/y/?]

AT-LAN-TEC/RealTek pocket adaptor support (CONFIG_ATP) [N/y/?]

(NEW) D-Link DE600 pocket adaptor support (CONFIG_DE600) [N/y/m/?] (NEW)

D-Link DE620 pocket adaptor support (CONFIG_DE620) [N/y/m/?] (NEW)

Token Ring driver support (CONFIG_TR) [N/y/?]

IBM Tropic chipset based adaptor support (CONFIG_IBMTR) [N/y/m/?] (NEW)

FDDI driver support (CONFIG_FDDI) [N/y/?]

Digital DEFEA and DEFPA adapter support (CONFIG_DEFXX) [N/y/?] (NEW)

ARCnet support (CONFIG_ARCNET) [N/y/m/?]

Enable arc0e (ARCnet "Ether-Encap" packet format) (CONFIG_ARCNET_ETH) [N/y/?] (NEW)

Enable arc0s (ARCnet RFC1051 packet format) (CONFIG_ARCNET_1051) [N/y/?] (NEW)

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Finally, in the file system section, the configuration script will ask you whether you want support for NFS, the networking file system. NFS lets you export file systems to several hosts, which makes the files appear as if they were on an ordinary hard disk attached to the host:

NFS file system support (CONFIG_NFS_FS) [y]

We describe NFS in detail in Chapter 14, The Network File System.

Linux 2.0.0 marked a significant change in Linux Networking. Many features were made a standard part of the Kernel, such as support for IPX. A number of options were also added and made configurable. Many of these options are used only in very special circumstances and we won't cover them in detail. The Networking HOWTO probably addresses what is not covered here. We'll list a number of useful options in this section, and explain when you'd want to use each one:

Basics

To use TCP/IP networking, you must answer this question with y. If you answer with n, however, you will still be able to compile the kernel with IPX support:

Networking options --›

[*] TCP/IP networking

Gateways

You have to enable this option if your system acts as a gateway between two networks or between a LAN and a SLIP link, etc. It doesn't hurt to enable this by default, but you may want to disable it to configure a host as a so-called firewall . Firewalls are hosts that are connected to two or more networks, but don't route traffic between them. They're commonly used to provide users with Internet access at minimal risk to the internal network. Users are allowed to log in to the firewall and use Internet services, but the company's machines are protected from outside attacks because incoming connections can't cross the firewall (firewalls are covered in detail in Chapter 9, TCP/IP Firewall):

[*] IP: forwarding/gatewaying

Virtual hosting

These options together allow to you configure more than one IP address onto an interface. This is sometimes useful if you want to do "virtual hosting," through which a single machine can be configured to look and act as though it were actually many separate machines, each with its own network personality. We'll talk more about IP aliasing in a moment:

[*] Network aliasing

‹*› IP: aliasing support

Accounting

This option enables you to collect data on the volume of IP traffic leaving and arriving at your machine (we cover this is detail in Chapter 10, IP Accounting):

[*] IP: accounting

PC hug

This option works around an incompatibility with some versions of PC/TCP, a commercial TCP/IP implementation for DOS-based PCs. If you enable this option, you will still be able to communicate with normal Unix machines, but performance may be hurt over slow links:

- - (it is safe to leave these untouched)

[*] IP: PC/TCP compatibility mode

Diskless booting

This function enables Reverse Address Resolution Protocol (RARP). RARP is used by diskless clients and X terminals to request their IP address when booting. You should enable RARP if you plan to serve this sort of client. A small program called rarp, included with the standard networking utilities, is used to add entries to the kernel RARP table:

‹*› IP: Reverse ARP

MTU

When sending data over TCP, the kernel has to break up the stream into blocks of data to pass to IP. The size of the block is called the Maximum Transmission Unit , or MTU. For hosts that can be reached over a local network such as an Ethernet, it is typical to use an MTU as large as the maximum length of an Ethernet packet - 1,500 bytes. When routing IP over a Wide Area Network like the Internet, it is preferable to use smaller-sized datagrams to ensure that they don't need to be further broken down along the route through a process called IP fragmentation . [19] Remember, the IP protocol can be carried over many different types of network, and not all network types will support packet sizes as large as Ethernet. The kernel is able to automatically determine the smallest MTU of an IP route and to automatically configure a TCP connection to use it. This behavior is on by default. If you answer y to this option this feature will be disabled.