A Request for Comments (RFC) is a publication of the Internet Engineering Task Force (IETF) and the Internet Society, the principal technical development and standards-setting bodies for the Internet.

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21
votes
4answers
16k views

DNS using CNAMEs breaks MX records?

We are trying to move all our websites we host to CNAMES as we are planning on moving servers in the new year and would like the ability to move some clients to one server and other clients somewhere ...
0
votes
1answer
167 views

ICMP replies - ingress or egress interface (e.g. from a traceroute)

When a traceroute is initiated and receives an ICMP reply from the nodes, which interface should the be replying be from according to RFC 1812. they are actually replying from ingress (where they ...
1
vote
1answer
1k views

What does this SAP error mean? recv104 NiIReadrecv nixxi.cp5087

I have an SAP BI Portal system and an SAP BW system. In the Visual Administrator of the BI Portal, section 'JCo RFC Provider' I have created some RFC listeners. In the SAP BW system (in transaction ...
0
votes
1answer
30 views

Creating a RFC 1123 compliant date for HTTP header creation on the CLI

I'm trying to create a HTTP 1/1 compliant date header using standard unix date(1) in order to post this to a RESTful server using curl or similar. Any ideas what format to pass to date(1) to get this ...
0
votes
0answers
30 views

IMAP woes when moving to new Exchange

We've recently moved to a semi-outsourced Exchange farm, replacing our internal one. An application I've been asked to help troubleshoot uses IMAP to download some emails from the Exchange servers in ...
9
votes
2answers
333 views

RFC that requires DNS servers to respond to unknown domain requests

My domain registrar and DNS provide currently ignores DNS requests to unknown domains. By ignore I mean black-holes and never responds which causes my DNS clients and resolver libraries to retry, ...
35
votes
4answers
43k views

What's the maximum URL length in Tomcat?

And is it configurable? Can I set up Tomcat so that a URL with, say, 200K of query params goes through successfully to the contained servlet? Yes, I know one should use POST when you have lots of ...
1
vote
1answer
156 views

Sendmail support of empty group addresses (AKA list syntax)

E-mail group addresses such as undisclosed-recipients:; or a group:<u1@example.net>,<u@x.example.net>; are valid forms of addressing according to RFC 5322, see for instance the ...
40
votes
2answers
2k views

Which RFCs should be cited as internet standards?

It's extremely common for RFCs to be cited in support of opinions (including Serverfault Q&A's), but the average IT employee has a very poor understanding in regards to which RFCs define standards ...
2
votes
2answers
620 views

IPv6 and Hop Limit

I am reading RFC 2460 about IPv6 and it says that "the packet is discarded if Hop Limit is decremented to zero.", so that is to say that if a router decrements a packet's Hop Limit to 0, other another ...
-1
votes
2answers
17 views

Is RFC1035s definition of a <domain-name> wrong?

[RFC1035] defines <domain-name> as <domain-name> is a domain name represented as a series of labels, and terminated by a label with zero length. This means a <domain-name> must be ...
1
vote
2answers
3k views

Does the OS X DHCP client support classless static routes (RFC3442)?

Simply put: does Mac OS X support RFC3442? RFC3442 implements DHCP codes (121 and 249) to provide classless static routes to DHCP clients. I can only seem to find rather old information circa 2005-...
18
votes
2answers
1k views

Why is RFC 7505 (Null MX) necessary?

IETF RFC 7505 describes MX records for a domain/host that explicitly should not receive email. This is accomplished by pointing the MX at the Domain Name System root. For example, nomail.example.com. ...
1
vote
2answers
100 views

Is smart hosting to an A record a violation of RFC-5321 section 1?

I have a sendmail server configured to smarthost to a downstream resource. The configuration is currently: define(`SMART_HOST',`relay:[vip.example.local]')dnl Since it's sending the A record for ...
1
vote
0answers
88 views

Unable to get structured data in logged messages even after adding mmpstrucdata and mmrfc5424addhmac?(RFC5424)

I am trying to log messages with structured data . But it is showing null value for structured data. I am working with rsyslog 8.9.0.Can someone tell me either i need to load some module or modify ...
5
votes
2answers
249 views

What is the difference between 3-digit and dotted SMTP error codes?

When looking up SMTP error codes, I sometimes see "550", or "5.5.0". And sometimes the number in the dotted code is different. I found the numeric codes defined in RFC 821 and the dotted codes in RFC ...
27
votes
1answer
3k views

How does the DNS protocol switch from UDP to TCP?

Before anyone asks: I've seen When do DNS queries use TCP instead of UDP? and it doesn't answer my question. All I keep hearing is "if the answer is too long, DNS will use TCP". This does not explain ...
1
vote
1answer
80 views

Is Strict-Transport-Security HTTP header name case-sensitive?

I'm digging into the HTTP Strict-Transport-Security specification, https://tools.ietf.org/html/rfc6797 It specifies the syntax of the header like this: Strict-Transport-Security: max-age=15768000 ; ...
-2
votes
1answer
110 views

Apache set max Content-Range

The Question: Client asks for: Range:bytes=0- Server responds with: Content-Length:8396748 Content-Range:bytes 0-8396747/8396748 I want to limit that Content-Range to 1MB chunks so the server ...
3
votes
0answers
587 views

Does a ping to 127.0.0.1 hit the network card? Which RFC / standard states that? [closed]

I recently did an exam where one of the questions stated that you can run ping 127.0.0.1 on a computer to verify if its network card is working. I have already read on multiple sources that this ...
5
votes
3answers
99 views

What to do if one doesn't want to receive email bounces?

Background—the standards RFC 5321 §4.5.5 states: All other types of messages (i.e., any message which is not required by a Standards-Track RFC to have a null reverse-path) SHOULD be sent with ...
4
votes
1answer
472 views

Replacing an MX record with a CNAME that doesn't match the hostname

Today we have 5 companies that all use Google for email services example1.com. 3w IN MX 10 mail.Google.com. example2.com. 3w IN MX 10 mail.Google.com. example3.com....
4
votes
2answers
121 views

In SMTP, how does one choose between “Accept than Bounce” vs “Bounce at the edge”?

There seems to be a variety of implementations of SMTP that either immediately reject a message, and others that do an accept, then bounce the message. Operationally, the accept-than-bounce is a ...
11
votes
7answers
4k views

Check public DNS health and RFC compliance

Every now and again I like to run checks on my DNS servers to make sure they are running right and to RFC spec. I used to use the DNSTools website to do this as it gave me a pretty good picture of ...
0
votes
1answer
26 views

RFC5321 “receiver should check […] reply code” (why?)

In SMTP commands are sent by the sender and responses which all begin with a numeric code are sent by the receiver. but then there's this bit: RFC5321 sec4.2 Whenever possible, a receiver- SMTP ...
2
votes
0answers
538 views

Why does RFC 2181 disallow MX record with a CNAME exchange?

According to RFC 2181 http://tools.ietf.org/html/rfc2181#section-10.3 10.3. MX and NS records The domain name used as the value of a NS resource record, or part of the value of a MX ...
0
votes
1answer
159 views

Different throughput Ethernet-Wireless Wireless-Ethernet

I've built an open source implementation of RFC2544 to test IPv4 network devices. One of the first devices I tested is a wireless router D-Link 2640B. In order to measure its performance I use a ...
8
votes
1answer
205 views

Is there an official limit to nameserver indirection?

Glue records are typically unavailable if a domain and its nameserver don't share a TLD, and technically aren't required if they don't share the same second-level domain, which could lead to extra ...
1
vote
1answer
444 views

How to exclude LAN traffic from IPSEC policy

I am trying to replace a Firewall/VPN appliance (Snapgear SG300) with another (Mikrotik RB951G-2HnD). My current router works, but, for the new mikrotik router, when I add the phase 2 tunnel, I can ...
1
vote
0answers
192 views

IPv6 and AdvManagedFlag

RA messages have AdvManagedFlag. If this flag is ON then host "should use stateful autoconfiguration to obtain addresses" (RFC 2462). But RA messages are processing by the kernel. How do we know that ...
8
votes
7answers
1k views

Best choice of private addresses for a “device area network”

I'm building an appliance consisting of several subdevices connected by ethernet inside the appliance. The appliance will connect to the customer network. The customer network can be using private ...
5
votes
2answers
6k views

Does the presence of a Content-ID header in an email MIME mean that the attachment must be embedded?

Two different third-party email products we have are reacting differently to the presence of a content-id header in the MIME source of an email. This is resulting in an inconsistent user experience ...
10
votes
2answers
2k views

SMTP allows for multiple FROM addresses in the RFC. Was this ever useful, why does this exist?

SMTP allows for multiple FROM addresses on the body (not the envelope) according to the RFCs. Has this feature ever been used for a legitimate purpose? Is it safe to discard messages that have ...
17
votes
2answers
763 views

RFC 1918 address on open internet?

In trying to diagnose a failover problem with my Cisco ASA 5520 firewalls, I ran a traceroute to www.btfl.com and, much to my surprise, some of the hops came back as RFC 1918 addresses. Just to be ...
0
votes
1answer
1k views

Qmail / Zend Mail - RFC 5322 compliant

My company is getting spammed by itself, or rather by it's Qmail, we've got a few automated processes sending out e-mails with Qmail and Zend Mail. I'm not a expert in either of these, (I know ...
11
votes
4answers
13k views

Legitimate reasons SMTP “MAIL FROM:” will not match “From:” Header in DATA

Is there ever a legitimate reason for the SMTP “MAIL FROM:” field to not match the “From:” field in the DATA section of a message, besides mailing lists? From http://stackoverflow.com/questions/...
4
votes
1answer
875 views

What encoding is used for non English languages in an email subject?

I'm writing a specification that essentially requires ASCII characters in an email message. I do recall that an email message can have a subject encoded in a foreign language, however I don't know ...
1
vote
1answer
81 views

Advertise NO-SOLICITING (RFC3865)

Does it bring anything to specify the Solicitation class keywords in Advertise NO-SOLICITING as per RFC-3865? For instance: dom.spammer:ADLT,dom.listing:ADV
0
votes
3answers
247 views

Is HTML content permitted in email header values?

In the process of troubleshooting an email message display issue, I noticed that an email header contained HTML. Example: From: <bob@foo.com> To: <john@foo2.com> Date: 11 Feb 13 12:00:...
0
votes
1answer
204 views

SMTP - Routing in RFC 821 and RFC 2821

RFC 821 indicates that the MAIL verb can be given a <forward-path> argument of the form "@ONE,@TWO:JOE@THREE" to indicate intermediate routing hosts (@ONE,@TWO) and the final receiver of the ...
0
votes
3answers
563 views

How is mail delivered to an account different than specified in To header? [duplicate]

Possible Duplicate: How can email possibly be routed to the right place with no to: address? I've seen this quite a few times now. I will receive an email at a domain that I manage (colin@...
1
vote
1answer
1k views

IP-Multicast difference between 224.0.0.1-255 and 239.0.0.0/8 block

Whats the difference between: Local subnetwork Addresses in the range 224.0.0.0 to 224.0.0.255 are individually assigned by IANA and designated for multicasting on the local subnetwork only. ...
1
vote
2answers
236 views

Is there a common X-Header for RFC 2821 “MAIL FROM”? Should it be DKIM signed?

w.r.t. the difference between RFC2821 MAIL From and RFC2822 FROM I'm considering having my MTA add a header specifying what was sent in the MAIL FROM portion of the envelope. The RFC2821 header is ...
5
votes
1answer
716 views

Is there an RFC or standard for “Envelope Journaling”?

Is there a formal standard defined for Envelope Journaling (or BCC journaling)? I'm a software developer, and want to make sure I implement the journaling consumer correctly. My model for reference ...
3
votes
1answer
148 views

Stateful IPv6 configuration when router is absent on link

RFC 2462 specifies: 5.5.2. Absence of Router Advertisements If a link has no routers, a host MUST attempt to use stateful autoconfiguration to obtain addresses and other configuration ...
-1
votes
1answer
499 views

Routing RFC1918 addresses through dd-wrt via a switch

I am a bit stuck with an experiment of mine. I have a network looking somewhat like this. | Internet | | ---- |Switch| ---- | | Server w/pub IP |...
3
votes
1answer
668 views

Is there a set of RFC's that every admin should know about? [closed]

Reading through the RFC's can result in finding very interesing and important topics that any sysadmin would deem useful. I also sometimes find it to be a good cure for insomnia reading through it, ...
1
vote
2answers
675 views

FreeBSD slow transfers - RFC 1323 scaling issue?

I think I may be having an issue with window scaling (RFC 1323) and am hoping that someone can enlighten me on what's going on. Server: FreeBSD 9, apache22, serving a static 100MB zip file. 192.168....
10
votes
2answers
6k views

Are two periods allowed in the local-part of an email address?

A third-party email gateway relay is refusing to process a message for an email address we're sending to. The address is in the format of firstname..lastname@recipientdomain.com (note the two periods)...
3
votes
3answers
3k views

SLAAC and DNS, no really - what's the deal?

So I know that there are extensions to SLAAC in the works to enable DNS discovery via RAs (RFC 6106). But what was the original intent? How did the IPv6 designers envision things working without DNS?...