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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18
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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
37 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 ...
0
votes
0answers
49 views

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

When a traceroute is initiated and receives an ICMP replies from the nodes, which interface should the be replying from according to RFC 1812. they are actually replying from ingress (where they ...
25
votes
1answer
2k 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
26 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 ; ...
1
vote
0answers
35 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 ...
-2
votes
1answer
91 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 ...
2
votes
0answers
158 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
85 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
422 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. ...
0
votes
1answer
22 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
285 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
127 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
155 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
657 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 ...
1
vote
1answer
301 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
118 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
958 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 ...
8
votes
2answers
765 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 ...
0
votes
1answer
844 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 ...
4
votes
2answers
117 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 ...
4
votes
1answer
678 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 ...
17
votes
2answers
597 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 ...
9
votes
4answers
6k 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 ...
1
vote
1answer
71 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
217 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 ...
0
votes
1answer
170 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
366 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 ...
1
vote
1answer
957 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
201 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 ...
3
votes
1answer
141 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
416 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 ...
5
votes
1answer
524 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
492 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, ...
4
votes
2answers
4k 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 ...
1
vote
2answers
596 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. ...
9
votes
2answers
4k 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 ...
2
votes
3answers
2k 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 ...
1
vote
3answers
1k views

How to configure bind for a private subdomain?

I am attempting to define a subdomain for a private network (RFC1918) behind a NAT firewall; let's call it priv.example.com. Normally, and from what I can gather on various websites, this could be ...
0
votes
3answers
3k views

Hotmail wants me to modify my SPF record

This is my current SPF record. It works well with gmail and yahoo but hotmail was ignoring. So i used their submit system and now they replied me with the text below. This is my current spf v=spf1 a ...
1
vote
1answer
358 views

setting up subdomain in IIS/DNS - possible incorrect subdomain structure

I am trying to create a subdomain in DNS, however it doesn't appear to be working. I am getting the standard Unable to determine IP address from host name for aa.00.website.com The domain name does ...
4
votes
1answer
812 views

Cisco ASA 5505, tcp window scaling (rfc1323)

I have a very odd issue with our cisco firewall, If on our osx machines we run the following to disable window scaling support: sudo sysctl -w net.inet.tcp.rfc1323=0 We see near 40% ...
9
votes
3answers
871 views

Is quoted-printable enough to make a mail compliant with the line-length-restriction posed in RFC 2822?

In RFC 2822 (defining E-Mail) is defined, that no line SHOULD be longer than 78 chars (excluding CRLF) and MUST not longer than 998 characters. With quoted-printable longer lines will be broken into ...
6
votes
3answers
3k views

Where is the documentation that states TCP and UDP source port should be over 1024 and random?

I am having a hard time to find where it is documented that the source port should be random and in the range 1024-65535. In which RFC is this documented? Edit: First reference for privileged ports ...
9
votes
1answer
6k views

What is the point of the zones.rfc1918 file for Bind9?

Using an Ubuntu 10.04 LTS server in a standalone environment and trying to use views to serve two different subnets of clients. Getting errors regarding the zones.rfc1918 file, so I'd like to know ...
5
votes
2answers
224 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 ...
4
votes
2answers
746 views

Formal separation marker of syslog events?

I've been looking at RFC5424 to find the formally specified marker that will end a syslog event. Unfortunately I couldn't find it. So If I wanted to implement some small syslog server that reacts on ...
2
votes
2answers
460 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
vote
1answer
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 ...
0
votes
5answers
356 views

Help me understand Public/Private IP space and NAT

I just started working at a small-medium sized business after graduating school. So much of my knowledge is high level concepts without a lot of hands on. My understanding that according to rfc1918 ...