From 1c3d8b89cb6cc12b794bb6ee2b753392809f2e84 Mon Sep 17 00:00:00 2001 From: Jet Hughes Date: Tue, 4 Apr 2023 15:20:38 +1200 Subject: [PATCH] vault backup: 2023-04-04 15:20:38 --- content/notes/11-DHCP.md | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/content/notes/11-DHCP.md b/content/notes/11-DHCP.md index bd1ff4c95..a71901ed1 100644 --- a/content/notes/11-DHCP.md +++ b/content/notes/11-DHCP.md @@ -14,6 +14,14 @@ Address Assignment - Allow direct network booting - Like RARP, constrained to single subnet, but perform at UDP/IP, instead of MAC layer +> [!INFO] RARP +> given mac address it finds the ip address. the opposite of ARP + +> [!INFO] ARP +> we need arp because we need the data link layer protocol. so we need the destination mac address. this allows us to send ethernet frame to a MAC address + +> [!INFO] BOOTP + DHCP - Dynamic Host Configuration Protocol (DHCP) - Compatible with BOOTP (uses same ports) @@ -23,6 +31,13 @@ DHCP - Limited to a single subnet, but routers can incorporate relay agents - Successor: DHCPv6, less useful in IPv6 +> [!INFO] DHCP +> more widely used. more compatible and generalised +> gives not only address. also tell you what is DNS server and gateway. +> ubiquitious +> radvd and slacc similar to DHCPv6 +> send broadcast message to network. the server takes these broadcast messages and returns and IP address, and the lease time of the address. broadcaster sends another messages to accept/reject the offer. this sequence of messages has a session ID + Static vs. Dynamic - Static address is assigned manually by system admin in the DHCP configuration file using the client’s MAC address - Server machines’ addresses should be static @@ -30,6 +45,8 @@ Static vs. Dynamic - Dynamically allocated address can be assigned to the same client as it keeps a table of past IP addresses and their clients MAC addresses. - Layer 3 (IP) change breaks existing connections if IP addresses change in a long session such as downloaders, terminal sessions +> [!INFO] + How DHCP Works - Client broadcasts UDP request to 255.255.255.255 port 67 - Routers can relay using a relay agent @@ -106,3 +123,14 @@ S.D. with DHCP - Requires client support, in DHCP client or application - You can provision based on the machine or subnet, or a single group +S.D. with DNS-SD +- Service (SRV) records specify service type, transport protocol, and the domain. +- _smtp._tcp.domain returns Priority, Weight, Port and Address of mail servers, for browsing. + - DNS Service Discovery (DNS-SD) allows for browsing service instances. + - Most commonly used with mDNS. +- Not suitable for very dynamic data in traditional DNS. Why? + +DNS-SD Example +- Examples taken from draft DNS-SD standard. +- What services are available on dns-sd.org? (provides a discovery starting point) dig +short -t any _services._dns-sd._udp.dnssd.org _ftp._tcp.dns-sd.org. _ssh._tcp.dns-sd.org. (and others...) +- What FTP services are available on dnssd.org? dig +short -t any _ftp._tcp.dnssd.org Apple\032QuickTime\032Files._ftp._tcp.d ns-sd.org. (and others...) \ No newline at end of file