How did Ned get people to buy into the story that Jon was his bastard?

[Angel Eyes]

If R+L=J, how did Ned convince people from Dorne to the Wall that Jon Snow was his bastard son conceived while on campaign? Jon must have been pretty small for an infant to disguise the fact that he was probably conceived several months before Ned came south from Winterfell with the North at his back and to be born as Ned reached Dorne. Was it just what people wanted to believe about Ned Stark, that the uptight and honorable Stark had fallen victim to lust? And how did he convince Catelyn to the point that she didn’t try going to Starfall to ask questions about the Daynes?

[Tywin Manderly]

28 minutes ago, Angel Eyes said:

If R+L=J, how did Ned convince people from Dorne to the Wall that Jon Snow was his bastard son conceived while on campaign? 

Ned does not need to convince anyone. He is the Warden of the North and on his home turf he can browbeat anyone into submissive silence. Catelyn, as well as various servants at Winterfell, can tell you all about that. It also helps that people below the Neck view the North as a remote grey waste about which they care little.

In addition is it in Westeros considered rude to pry into the origins of someone's bastard and nobody is going to run the risk of incurring the wrath of a Great Lord for something as trival and common as a lord's bastard.

[Megorova]

People believed him, because they had no reason to think, that Ned lied about fathering a bastard. If he didn't cheated Cat, then why did he said that he did? Why would he take a blame, and suffer repercusions, if he was not guilty in adultery? Ned himself said, that the baby is his. Furthermore, that baby looked even more Stark than Robb. The supposed father said, that the baby is his, and they look alike, so there was no reason for people to think otherwise. Also, probably, Ned lied about, when exactly Jon was born, and conceived. My guess, is that actually Jon is older, and that he was conceived while Ned was still in The Vale, or on his way from there to The North. That's why people think, that bastards grow faster - Ned's maester made it up, to explain, why Jon is bigger and looks older that Robb, even though supposedly Robb is older. Because, according to Ned's story, Jon was conceived after his wedding with Cat, and was born later than Robb, which is a lie.

So, basically, there are three reasons, why no one ever suspected - 1. Jon's age is "fixed", 2. he looks like Ned, 3. Ned said that Jon is his son.

Also, none of them ever suspected, that Ned could be lying for some mysterious reason, because they were medieval people, in their world there's no TVs, Google, Wikipedia, and other modern-world sources of information, that provide people with access to nearly unlimited knowledge, and make them more educated about the world around them, and what exists in it. Unlike modern people of the real world, GRRM's characters are simple people, with simple minds, and limited imagination, that are living in a simple and small world. Why Robb and Cat were unable to predict The Red Wedding? Why the Great Masters of Astapor didn't suspected, that Dany will use her newly bought Unsullied to seize their city? -> Because they were unable to imagine, that someone will try to do something like that, that something like that is even possible. The same applies to the case, why no one ever suspected, that Jon is not Ned's bastard. Those people had simple minds, and limited life experience, so they had no reasons/basis to think, that Ned Stark can have a reason to lie about Jon.

[Euron III Greyjoy]

I think people just didn't really care. Robert's Rebellion had just finished, and a new House was in charge of the 7 Kingdoms. Not to mention thousands upon thousands of people where dead. Who's going to look twice at some Lord's bastard? Especially with all that shit going on in the background.

[Trigger Warning]

3 hours ago, Angel Eyes said:

Catelyn to the point that she didn’t try going to Starfall to ask questions about the Daynes?

 

That's a pretty huge commitment for something that ultimately doesn't matter, he says it's his bastard and lots of lords have bastards. The reality is that it's just not that suspicious, it's only suspicious to the fanbase because they suspect R+L=J. 

[nyser1]

A 19/20 year old male from a prominent family who went to war for a prolonged period time and was recently married (to someone he just met and was betrothed to his brother) had a bastard. Not to hard to conceive. Throw in the Ashara rumors and voila.

[corbon]

4 hours ago, Angel Eyes said:

If R+L=J, how did Ned convince people from Dorne to the Wall that Jon Snow was his bastard son conceived while on campaign?

I don't think Ned 'convinced' anybody. I think mostly people saw Ned's actions and made assumptions that seemed to be confirmed by more actions and the odd word..

4 hours ago, Angel Eyes said:

Jon must have been pretty small for an infant to disguise the fact that he was probably conceived several months before Ned came south from Winterfell with the North at his back and to be born as Ned reached Dorne.

Err, no. Jon would have been conceived several months into the war. He is accepted by all to be younger than Robb, who was conceived in the Riverlands after the Battle of the Bells. Robb and Jon were together at a very early age and you can't fool people who are around very young babies about such things, because regardless of size, the changes and developmental milestones are massive and fairly consistent in the first 6 months. Its not possible for Jon to be more than a month or two older than Robb.
The early part of the war seems to have a very compressed timespan, with the battle of the Bells possibly around months 3 or 4 into the war. Robert fights several battles (obviously quite small ones) very early on, and then gets shunted north when losing to the Tyrell van, then Battle of the Bells he is still on the run and wounded, but not yet joined up with his allies.
I think its likely that most of the early battles, including the Battle of the Bells, are fought largely with mostly the relatively small semi-permanently embodied forces of Lords, Knights and their households, with the full levies still not raised and trained and in place. Hence the compressed timescale, fast movements (add in GRRM being poor with grand logistics here) and relatively small battles. This also accounts in large part for the apparent lull after the Battle of the Bells until Rhaegar marches to the Trident - the Rebels need time for their levies to be gathered and march south and be trained, and by the time they got there the Loyalists have reformed enough so the rebels are still not strong enough to take KL. Plus you have diplomacy etc going on with the Lannisters and Greyjoys. Its notable that after the Battle of the Bells its actually the loyalists who make the next major move we know of - Rhaegar marching north and being met at the Trident.

4 hours ago, Angel Eyes said:

Was it just what people wanted to believe about Ned Stark, that the uptight and honorable Stark had fallen victim to lust?

I'm sure thats a significant part of it, especially for Robert. But not 'just' that.
The fact is that
i) most people don't care.
ii) there is a ready answer available that is both salacious and gossipy and more or less meaningless
iii) its actually literally irrelevant to anyone except Jon. Catelyn is only bothered because Ned treats Jon better than would be expected, and she is insecure at the time due to her position
iv) Ned is neither confirming nor denying any rumour, enabling people to feel satisfied once they have an answer that works for them (if they even care).

4 hours ago, Angel Eyes said:

And how did he convince Catelyn to the point that she didn’t try going to Starfall to ask questions about the Daynes?

Why would she go there? And what for? 
She herself thinks that its entirely normal, and entirely forgivable, for Ned to have conceived a bastard on campaign. The unforgivable thing is that he brought the bastard home and raised him with the family, which does two things. i) it shows the world her 'shame' (which she wouldn't be shamed at if it wasn't so public) constantly, ii) it gives the bastard a great deal more political currency for him or his heirs to challenge her progeny down the line (a bastard raised as part of the Lords family has a great deal more going for him than one raised outside the family, or outside nobility).
Meanwhile, Ashara (the suspect mother) is dead. What is there to learn? And in the north she has he own family to raise and household to keep, not to mention husband-who-is-practically-a-stranger to secure. Traipsing off to Dorne to find out about the bastard would be ridiculous in multiple ways.

Ned didn't convince her of anything. He literally frightened her into shutting up about it and left her wondering forever.

[LynnS]

I'm reminded of this:
 

Quote

 

A Game of Thrones - Eddard VIII

It struck him suddenly that he might return to Winterfell by sea. Ned was no sailor, and ordinarily would have preferred the kingsroad, but if he took ship he could stop at Dragonstone and speak with Stannis Baratheon. Pycelle had sent a raven off across the water, with a polite letter from Ned requesting Lord Stannis to return to his seat on the small council. As yet, there had been no reply, but the silence only deepened his suspicions. Lord Stannis shared the secret Jon Arryn had died for, he was certain of it. The truth he sought might very well be waiting for him on the ancient island fortress of House Targaryen.

And when you have it, what then? Some secrets are safer kept hidden. Some secrets are too dangerous to share, even with those you love and trust. Ned slid the dagger that Catelyn had brought him out of the sheath on his belt. The Imp's knife. Why would the dwarf want Bran dead? To silence him, surely. Another secret, or only a different strand of the same web?

 

 

[Thomaerys Velaryon]

Even Catelyn Stark is ok with Ned having a bastard. She is just not ok with him being raised at Winterfell.

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Many men fathered bastards. Catelyn had grown up with that knowledge. It came as no surprise to her, in the first year of her marriage, to learn that Ned had fathered a child on some girl chance met on campaign. He had a man's needs, after all, and they had spent that year apart, Ned off at war in the south while she remained safe in her father's castle at Riverrun. Her thoughts were more of Robb, the infant at her breast, than of the husband she scarcely knew. He was welcome to whatever solace he might find between battles. And if his seed quickened, she expected he would see to the child's needs.

He did more than that. The Starks were not like other men. Ned brought his bastard home with him, and called him "son" for all the north to see. When the wars were over at last, and Catelyn rode to Winterfell, Jon and his wet nurse had already taken up residence.

AGOT, Catelyn II

She is not ok with Jon being raised at Winterfell because she is afraid her own grandchildren's claim on the castle could be contested if Jon marries a noblewoman and fathers trueborn sons.

Quote

Ned looked shocked. "He asked to join the Night's Watch?"

Catelyn said nothing. Let Ned work it out in his own mind; her voice would not be welcome now. Yet gladly would she have kissed the maester just then. His was the perfect solution. Benjen Stark was a Sworn Brother. Jon would be a son to him, the child he would never have. And in time the boy would take the oath as well. He would father no sons who might someday contest with Catelyn's own grandchildren for Winterfell.

AGOT, Catelyn II

[Universal Sword Donor]

6 hours ago, Angel Eyes said:

And how did he convince Catelyn to the point that she didn’t try going to Starfall to ask questions about the Daynes?

Lol who the hell is she going to ask? Ashara is dead. Ned Dayne isn't alive, and the story he hears is about Wylla. 

[Eden-Mackenzie]

“Honey, I’m home, I brought my sister’s bones, Willem Dustin’s horse, and my son Jon.”  Little did anyone realize, Ned was playing two truths and a lie...

 

Like everyone else has said, Ned didn’t need to convince anyone, he’s the honorable Eddard Stark, Lord of Winterfell, Warden of the North. If he says he has a bastard son, he must have a bastard son. I don’t recall anyone doubting Ned is Jon’s father, the only discussions have been trying to figure out who is the mother, which if anything is in line with Ned’s character - he isn’t someone who would unnecessarily ruin the reputation of the mother just to save himself. 

[Unacosamedarisa]

Just to add to what everyone else has said, there’s this from Littlefinger in ASOS...

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"I have no gallant knights in my service, Alayne. Such a tale would draw unwanted questions as a corpse draws crows. It is rude to pry into the origins of a man's natural children, however."

Also, the way I see it is, if the honourable Ned Stark is admitting or claiming to have a bastard, people are going to take it as the truth... otherwise why would he lie about it and besmirch his own honour?

[John Suburbs]

21 hours ago, Angel Eyes said:

If R+L=J, how did Ned convince people from Dorne to the Wall that Jon Snow was his bastard son conceived while on campaign? Jon must have been pretty small for an infant to disguise the fact that he was probably conceived several months before Ned came south from Winterfell with the North at his back and to be born as Ned reached Dorne. Was it just what people wanted to believe about Ned Stark, that the uptight and honorable Stark had fallen victim to lust? And how did he convince Catelyn to the point that she didn’t try going to Starfall to ask questions about the Daynes?

Most people couldn't imagine a lord admitting to fathering a bastard if it wasn't true. And by the time Ned shows up with Jon at Winterfell, which I believe is the first time he has even acknowledged his presence, the war is over, Lyanna, Rhaegar, and the MK are dead, Robert is installed on the throne and the new dynasty is underway.

The only person I think should have put two and two together here is Varys. I can only imagine that the whole time Rhaegar and Lyanna were together, Varys' primary thought was the emergence of yet another Targaryen bastard. The realm had just gotten rid of the last of the Blackfyres not 20 years earlier, so the arrival of a new one holds all kinds of implications for Varys regardless of whether he is a Targ, a Blackfyre or something else. So while most people might have not given a Stark bastard another thought, I think it definitely should have been something that made Varys go hmmmm . . .

Of course, this is invalidated if Rhaegar had nothing to do with Lyanna's abduction and they were never together at all. Varys would surely know if this was the case.

 

[Legitimate_Bastard]

15 hours ago, Universal Sword Donor said:

Lol who the hell is she going to ask? Ashara is dead. Ned Dayne isn't alive, and the story he hears is about Wylla. 

Plus, Cat is all about that duty.

A Clash of Kings - Catelyn VI

When the last of Edmure's foot had shuffled under the portcullis, Brienne asked, "What shall we do now, my lady?"

"Our duty." Catelyn's face was drawn as she started across the yard. I have always done my duty, she thought. Perhaps that was why her lord father had always cherished her best of all his children. Her two older brothers had both died in infancy, so she had been son as well as daughter to Lord Hoster until Edmure was born. Then her mother had died and her father had told her that she must be the lady of Riverrun now, and she had done that too. And when Lord Hoster promised her to Brandon Stark, she had thanked him for making her such a splendid match.

I gave Brandon my favor to wear, and never comforted Petyr once after he was wounded, nor bid him farewell when Father sent him off. And when Brandon was murdered and Father told me I must wed his brother, I did so gladly, though I never saw Ned's face until our wedding day. I gave my maidenhood to this solemn stranger and sent him off to his war and his king and the woman who bore him his bastard, because I always did my duty.

[The Commentator]

23 hours ago, Angel Eyes said:

If R+L=J, how did Ned convince people from Dorne to the Wall that Jon Snow was his bastard son conceived while on campaign? Jon must have been pretty small for an infant to disguise the fact that he was probably conceived several months before Ned came south from Winterfell with the North at his back and to be born as Ned reached Dorne. Was it just what people wanted to believe about Ned Stark, that the uptight and honorable Stark had fallen victim to lust? And how did he convince Catelyn to the point that she didn’t try going to Starfall to ask questions about the Daynes?

As you say, IF.  

I don’t believe in R+L=J and will simply say Ned convinced people because it was the truth.  The bastard is really his bastard.