clefor@secola.Columbia.NCR.COM (Cheryl LeFor) (01/12/90)
Hi!
I have some questions about some SNMP standards and would appreciate any
feedback from "those in the know."
I am writing some applications that will communicate with an SNMP agent in
order to retrieve mib variables. In one case, I retreive the mib Interface
Table entries. My question concerns the ifPhysAddress field of the ifTable.
According to the RFC which describes the mib (RFC 1066), ifPhysAddress is
defined as such:
OBJECT: ifPhysAddress { ifEntry 6 }
Syntax: OCTET STRING
Definition:
The interface's address at the protocol layer immediately "below"
IP in the protocol stack.
My question is: What is the standard format for this octet string?
6 byte phys addr: 080014118562
OR, character string: "08:00:14:11:85:62"
This question also pertains to the Address Translation Table atPhysAddress
field (OCTET STRING).
With the particular SNMP agent I'm using, ifPhysAddress came back in the
"08:00..." form, and atPhysAddress came back in the 6 byte form.
One last question...
(This is probably more for a Nysernet dude but here goes..)
WHY are the components of the mib path defined as unsigned longs? Isn't that
a lot of space for a number which is usually a one digit number?
iso.org.dod.internet.mgmt.mib
i.e.: 1.3.6.1.2.1 would have 6 unsigned longs.
Thanks for your time!!karl@asylum.SF.CA.US (Karl Auerbach) (01/12/90)
In article <469@secola.Columbia.NCR.COM> clefor@secola.UUCP () writes: >I have some questions about some SNMP standards and would appreciate any >feedback from "those in the know." You really ought to be posting this to snmp@nisc.nyser.net. >My question is: What is the standard format for this octet string? > 6 byte phys addr: 080014118562 > OR, character string: "08:00:14:11:85:62" The former -- the value is the binary value of the address. When we did the SMI we could have defined a special type, but that would have left an unending need to allocate types for all the different forms of addresses on all kinds of media. (In practice, the it really may not be that much of a problem as lots of things use 48-bit addresses.) >With the particular SNMP agent I'm using, ifPhysAddress came back in the >"08:00..." form, and atPhysAddress came back in the 6 byte form. Somebody is doing it wrong. However, you may want to look deeper as some manager/client-side programs either know that these items are special and know how to pretty-print them, or delve into the values to find the most human oriented way to print them. You might find that the value is being returned over-the-wire in the "correct" format but is being pretty-printed for you. >(This is probably more for a Nysernet dude but here goes..) >WHY are the components of the mib path defined as unsigned longs? Isn't that >a lot of space for a number which is usually a one digit number? I'm not a PSI (ne Nysernet) dude, but anyway... Some early SNMP implementations got into trouble by assuming that object identifier components are a single digit. Right off the bat you run into TCP and UDP port numbers as components, and these must be at least 16 bits (which can map into as many as three bytes in the ASN.1 encoded object identifier.) I'm starting to run into equipment where the number of instances is often in the thousands and a single byte just doesn't make it. I sure hope I'm being lucid -- I don't know what spirit is moving me to read mail at 4am. --karl-- Karl Auerbach Epilogue Technology Corp. Santa Cruz, California
mrose@CHEETAH.NYSER.NET (Marshall Rose) (01/13/90)
I think your message is more appropriately addressed to the snmp@nisc.nyser.net discussion group. Let's move this thread there. /mtr