The /proc filesystem is a very nice way of changing kernel parameters during runtime of the system. I have listed a couple of them below:
/:
/proc/version contains information about the running Linux. /proc/meminfo contains information about the memeory. /proc/swaps swap space information /proc/partitions lists all disk drive partitions on your system. /proc/cpuinfo lists characteristics of your system processor. /proc/pci lists information about the PCI devices on your system. /proc/interrupts lists information about the IRQs being used. /proc/dma lists information about the DMA channels being used. /proc/ioports lists the I/O port address ranges being used.
/net/:
/proc/net/dev contains statistics on the network interfaces. /proc/net/tcp or udp shows the open sockets. /proc/net/arp contains the ARP table. /proc/net/route contains the routing table. /proc/net/snmp contains protocol statistics.
/sys/net/ipv4/:
icmp_echo_ignoe_all ignore all PING requests.icmp_echo_ignoe_broadcast ignore all PING requests with a broadcast address.ip_forwardip_masq_debugtcp_syncookies Protection from "SYN" Attacks. Sends a syncookie, when the backlogqueue of the socket overflows.rp_filter On a router, this enables spoofed address filteringsecure_redirects Accept ICMP redirect messages only for gateways listed in the gateway list.log_martians Log packets with impossible addresses.accept_source_routeip_local_port_range Defines the portrange local services will be assigend to.
You can for example do the following:
echo 61000 65095 > /proc/sys/net/ipv4/ip_local_port_range