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Name Resolution in Network Management

Name Resolution in Network Management. A Quick Look at the Aspects of Naming and Name Resolution. What Is Name Resolution?. Used to translate the IP Address to a name. Provides a way of identifying resources by name rather than the address itself. The Components. /etc/hosts (Files)

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Name Resolution in Network Management

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  1. Name Resolution in Network Management A Quick Look at the Aspects of Naming and Name Resolution

  2. What Is Name Resolution? • Used to translate the IP Address to a name. • Provides a way of identifying resources by name rather than the address itself.

  3. The Components • /etc/hosts (Files) • /etc/networks (Files) • Domain Name Service (DNS) • Network Information Service (NIS) • Applications that use name resolution are dependent upon this working properly.

  4. Components of Network Node Manager Affected by Name Resolution • Maps • Discovery • Events • Tools and Applications • ECS and Correlation • SNMP Configuration

  5. What’s Legal in a Host Name? • According to RFC-1035 (STD13): • The labels must follow the rules for ARPANET host names. They must start with a letter, end with a letter or digit, and have as interior characters only letters, digits, and hyphen. There are also some restrictions on the length. Labels must be 63 characters or less. • Note that tildes, underscores,dots orpunctuation characters are not legal.

  6. DNS Names • Made up of a host name suffixed by domain and sub-domain labels separated by the dot character. • mail.southernview.com is the host mail, sub-domain southernview, within the domain of com.

  7. Network Node Manager Node Labels • 1) If the node supports IP: •   1a) If a non-migratable software loopback IP address(other than 127.0.0.1) exists on the node, and the address resolves to an IP hostname, that hostname is used. •   1b) Otherwise, NNM chooses the name associated with the lowest numbered non-migratable IP address that resolves to an IP hostname. • 1c) If no IP addresses resolve to an IP hostname, the lowest numbered non-migratable IP address is formatted as a string and used as the hostname. •   [ "lowest numbered" means when compared as integers. ] • [ "non-migratable" applies only to HP's Service Guard nodes; a migratable address is one that can migrate between systems in a Service Guard cluster. ]

  8. NNM Continued • 2) Otherwise, if the node supports IPX:  • 2a) If the node has an internal IPX server address (i.e. an address of the form <netnum>:000000000001), that address is formatted as a string and used as the hostname. • 2b) Otherwise, the lowest numbered IPX address is formatted as a string and used as the hostname.[ "lowest numbered" is determined by a byte-by-byte comparison ] •   3) Otherwise, if the node supports neither IP nor IPX, but has an LLA/MAC address, the address is formatted as a string and used as the hostname. The hostname is stored in object database's "IP Hostname" field, possibly making the name somewhat of a mis-nomer (it could be an IPX name). For interfaces, separate IP and IPX address fields exist.

  9. NNM Continued •  Node selection names are by default the same as the IP Hostname, though users and applications can change the selection name. If the selection names for two objects conflict, a numeric ID string is appended to one of the selection names in order to achieve uniqueness. • For node labels the rules are (applied in order): • 1) If the node has an IP hostname (see 1a and 1b under names above), then the label is the IP hostname truncated to just the basename. •   2) Otherwise, if the node is a NetWare server: •   2a) If the node has a NetWare Server Name, it is used as the label. •   2b) Otherwise, the label is the network number of the internal Server address (i.e. the 000000000001, which is the same for every server, is removed).

  10. NNM Continued •   3) Otherwise, if the node supports SNMP and reports a SNMP sysName value, that value is used as the label. •   4) Otherwise, if the node supports IP, an IP address is used as the label (see 1c in the "names" section). •   5) Otherwise, if the node supports IPX, the host-address portion of the IPX address is used as the label. The address is formatted to translate the vendor of the hardware. (E.g. 100:080009ABCDEF gets a label of "HP-ABCDEF"). •   6) Otherwise, if the node has a LLA/MAC, the physaddr formatting as described in (5) is performed and the result is used as the label.

  11. Proper Multi-Homed Host Naming • A single host name mapped to all IP Addresses • Each interface aliased as a separate hostname if needed. • For instance: • 10.1.1.1 router1 router1.unknowndomain.com e0-router1 • 10.1.2.1 router1 router1.unknowndomain.com e1-router1 • 10.1.3.1 router1 router1.unknowndomain.com s0-router1 • 10.1.4.1 router1 router1.unknowndomain.com s1-router1

  12. A Web Hosting Example • 10.1.1.10 web1 web1.unknowndomain.com nfs-web1 • 10.1.1.11 web1 web1.unknowndomain.comwww.customer1.com • 10.1.1.12 web1 web1.unknowndomain.com www.customer2.com • 10.1.1.13 web1 web1.unknowndomain.com www.customer3.com • 10.1.1.14 web1 web1.unknowndomain.com www.customer4.com • 10.1.1.15 web1 web1.unknowndomain.com www.customer5.com

  13. What Happens When Things Go Wrong • The Labels appear screwed up. • The Events DB takes a long time to load. • Problems with double-clicking on an event to go to a sub-map occur. • Pair-wise Correlation breaks. • Events lookup of a Node don’t show all of the events. • Discovery doesn’t work properly. • Nodes may show up as separate entities although they are part of a single node. • SNMPCollect doesn’t poll correctly. • Tools don’t work that are launchable to a Node. • The events show up slowly in some cases. • Community Strings become a nightmare to maintain. • The Application thrashes performance wise. • It can impair the performance of third party products.

  14. Process “Heavy Hitters” • Xnmevents – All events resolved from an IP Address to a Host Name • Netmon – IP Addresses are resolved to a Host Name for discovery & configuration checks. • SNMPCollect – If host names are used in the configuration, host names resolved back to IP Addresses. • Tools – Dependent upon ARFs definition of fields use. I.e. Telnet $OVSelection1

  15. Common Mistakes • Using illegal characters in a host name. • Treating each IP address / Hostname as an exclusive pair. • Having a forward lookup but not a backward entry. • Not maintaining the DNS Service database.

  16. Recommendations • If you use files, make them DNS or NIS ready. • Larger installations should use DNS locally. • Check your integration with the script checkDNS.ovpl in /opt/OV/support.

  17. Comments? Questions?

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